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/linux-master/fs/xfs/
H A Dxfs_inode.cdiff e23d7e82 Thu Mar 14 11:07:02 MDT 2024 Andrey Albershteyn <aalbersh@redhat.com> xfs: allow cross-linking special files without project quota

There's an issue that if special files is created before quota
project is enabled, then it's not possible to link this file. This
works fine for normal files. This happens because xfs_quota skips
special files (no ioctls to set necessary flags). The check for
having the same project ID for source and destination then fails as
source file doesn't have any ID.

mkfs.xfs -f /dev/sda
mount -o prjquota /dev/sda /mnt/test

mkdir /mnt/test/foo
mkfifo /mnt/test/foo/fifo1

xfs_quota -xc "project -sp /mnt/test/foo 9" /mnt/test
> Setting up project 9 (path /mnt/test/foo)...
> xfs_quota: skipping special file /mnt/test/foo/fifo1
> Processed 1 (/etc/projects and cmdline) paths for project 9 with recursion depth infinite (-1).

ln /mnt/test/foo/fifo1 /mnt/test/foo/fifo1_link
> ln: failed to create hard link '/mnt/test/testdir/fifo1_link' => '/mnt/test/testdir/fifo1': Invalid cross-device link

mkfifo /mnt/test/foo/fifo2
ln /mnt/test/foo/fifo2 /mnt/test/foo/fifo2_link

Fix this by allowing linking of special files to the project quota
if special files doesn't have any ID set (ID = 0).

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 0e24ec3c Thu Feb 22 01:33:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remember sick inodes that get inactivated

If an unhealthy inode gets inactivated, remember this fact in the
per-fs health summary.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
H A Dxfs_super.cdiff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff d8d222e0 Mon Jan 15 21:33:07 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: read only mounts with fsopen mount API are busted

Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:

[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.

Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.

The syscall trace is:

fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0

Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.

During mount instantiation, we call xfs_fs_validate_params() which
does:

/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}

and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:

/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);

With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.

However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.

Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes: 73e5fff98b64 ("xfs: switch to use the new mount-api")
cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
H A Dxfs_buf.cdiff 0b3a76e9 Mon Jan 15 15:59:46 MST 2024 Dave Chinner <dchinner@redhat.com> xfs: use GFP_KERNEL in pure transaction contexts

When running in a transaction context, memory allocations are scoped
to GFP_NOFS. Hence we don't need to use GFP_NOFS contexts in pure
transaction context allocations - GFP_KERNEL will automatically get
converted to GFP_NOFS as appropriate.

Go through the code and convert all the obvious GFP_NOFS allocations
in transaction context to use GFP_KERNEL. This further reduces the
explicit use of GFP_NOFS in XFS.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 0a97c01c Thu Nov 30 12:40:18 MST 2023 Nhat Pham <nphamcs@gmail.com> list_lru: allow explicit memcg and NUMA node selection

Patch series "workload-specific and memory pressure-driven zswap
writeback", v8.

There are currently several issues with zswap writeback:

1. There is only a single global LRU for zswap, making it impossible to
perform worload-specific shrinking - an memcg under memory pressure
cannot determine which pages in the pool it owns, and often ends up
writing pages from other memcgs. This issue has been previously
observed in practice and mitigated by simply disabling
memcg-initiated shrinking:

https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@gmail.com/T/#u

But this solution leaves a lot to be desired, as we still do not
have an avenue for an memcg to free up its own memory locked up in
the zswap pool.

2. We only shrink the zswap pool when the user-defined limit is hit.
This means that if we set the limit too high, cold data that are
unlikely to be used again will reside in the pool, wasting precious
memory. It is hard to predict how much zswap space will be needed
ahead of time, as this depends on the workload (specifically, on
factors such as memory access patterns and compressibility of the
memory pages).

This patch series solves these issues by separating the global zswap LRU
into per-memcg and per-NUMA LRUs, and performs workload-specific (i.e
memcg- and NUMA-aware) zswap writeback under memory pressure. The new
shrinker does not have any parameter that must be tuned by the user, and
can be opted in or out on a per-memcg basis.

As a proof of concept, we ran the following synthetic benchmark: build the
linux kernel in a memory-limited cgroup, and allocate some cold data in
tmpfs to see if the shrinker could write them out and improved the overall
performance. Depending on the amount of cold data generated, we observe
from 14% to 35% reduction in kernel CPU time used in the kernel builds.


This patch (of 6):

The interface of list_lru is based on the assumption that the list node
and the data it represents belong to the same allocated on the correct
node/memcg. While this assumption is valid for existing slab objects LRU
such as dentries and inodes, it is undocumented, and rather inflexible for
certain potential list_lru users (such as the upcoming zswap shrinker and
the THP shrinker). It has caused us a lot of issues during our
development.

This patch changes list_lru interface so that the caller must explicitly
specify numa node and memcg when adding and removing objects. The old
list_lru_add() and list_lru_del() are renamed to list_lru_add_obj() and
list_lru_del_obj(), respectively.

It also extends the list_lru API with a new function, list_lru_putback,
which undoes a previous list_lru_isolate call. Unlike list_lru_add, it
does not increment the LRU node count (as list_lru_isolate does not
decrement the node count). list_lru_putback also allows for explicit
memcg and NUMA node selection.

Link: https://lkml.kernel.org/r/20231130194023.4102148-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-2-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff e33c267a Tue May 31 21:22:24 MDT 2022 Roman Gushchin <roman.gushchin@linux.dev> mm: shrinkers: provide shrinkers with names

Currently shrinkers are anonymous objects. For debugging purposes they
can be identified by count/scan function names, but it's not always
useful: e.g. for superblock's shrinkers it's nice to have at least an
idea of to which superblock the shrinker belongs.

This commit adds names to shrinkers. register_shrinker() and
prealloc_shrinker() functions are extended to take a format and arguments
to master a name.

In some cases it's not possible to determine a good name at the time when
a shrinker is allocated. For such cases shrinker_debugfs_rename() is
provided.

The expected format is:
<subsystem>-<shrinker_type>[:<instance>]-<id>
For some shrinkers an instance can be encoded as (MAJOR:MINOR) pair.

After this change the shrinker debugfs directory looks like:
$ cd /sys/kernel/debug/shrinker/
$ ls
dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42
mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43
mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44
rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49
sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13
sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36
sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19
sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10
sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9
sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37
sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38
sb-dax-11 sb-proc-45 sb-tmpfs-35
sb-debugfs-7 sb-proc-46 sb-tmpfs-40

[roman.gushchin@linux.dev: fix build warnings]
Link: https://lkml.kernel.org/r/Yr+ZTnLb9lJk6fJO@castle
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lkml.kernel.org/r/20220601032227.4076670-4-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff b9b3fe15 Wed Apr 20 16:44:59 MDT 2022 Dave Chinner <david@fromorbit.com> xfs: convert buffer flags to unsigned.

5.18 w/ std=gnu11 compiled with gcc-5 wants flags stored in unsigned
fields to be unsigned. This manifests as a compiler error such as:

/kisskb/src/fs/xfs/./xfs_trace.h:432:2: note: in expansion of macro 'TP_printk'
TP_printk("dev %d:%d daddr 0x%llx bbcount 0x%x hold %d pincount %d "
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:5: note: in expansion of macro '__print_flags'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/xfs_buf.h:67:4: note: in expansion of macro 'XBF_UNMAPPED'
{ XBF_UNMAPPED, "UNMAPPED" }
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:40: note: in expansion of macro 'XFS_BUF_FLAGS'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/./xfs_trace.h: In function 'trace_raw_output_xfs_buf_flags_class':
/kisskb/src/fs/xfs/xfs_buf.h:46:23: error: initializer element is not constant
#define XBF_UNMAPPED (1 << 31)/* do not map the buffer */

as __print_flags assigns XFS_BUF_FLAGS to a structure that uses an
unsigned long for the flag. Since this results in the value of
XBF_UNMAPPED causing a signed integer overflow, the result is
technically undefined behavior, which gcc-5 does not accept as an
integer constant.

This is based on a patch from Arnd Bergman <arnd@arndb.de>.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff b9b3fe15 Wed Apr 20 16:44:59 MDT 2022 Dave Chinner <david@fromorbit.com> xfs: convert buffer flags to unsigned.

5.18 w/ std=gnu11 compiled with gcc-5 wants flags stored in unsigned
fields to be unsigned. This manifests as a compiler error such as:

/kisskb/src/fs/xfs/./xfs_trace.h:432:2: note: in expansion of macro 'TP_printk'
TP_printk("dev %d:%d daddr 0x%llx bbcount 0x%x hold %d pincount %d "
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:5: note: in expansion of macro '__print_flags'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/xfs_buf.h:67:4: note: in expansion of macro 'XBF_UNMAPPED'
{ XBF_UNMAPPED, "UNMAPPED" }
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:40: note: in expansion of macro 'XFS_BUF_FLAGS'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/./xfs_trace.h: In function 'trace_raw_output_xfs_buf_flags_class':
/kisskb/src/fs/xfs/xfs_buf.h:46:23: error: initializer element is not constant
#define XBF_UNMAPPED (1 << 31)/* do not map the buffer */

as __print_flags assigns XFS_BUF_FLAGS to a structure that uses an
unsigned long for the flag. Since this results in the value of
XBF_UNMAPPED causing a signed integer overflow, the result is
technically undefined behavior, which gcc-5 does not accept as an
integer constant.

This is based on a patch from Arnd Bergman <arnd@arndb.de>.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 01728b44 Thu Mar 17 10:09:13 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight

I've been chasing a recent resurgence in generic/388 recovery
failure and/or corruption events. The events have largely been
uninitialised inode chunks being tripped over in log recovery
such as:

XFS (pmem1): User initiated shutdown received.
pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
XFS (pmem1): Unmounting Filesystem
XFS (pmem1): Mounting V5 Filesystem
XFS (pmem1): Starting recovery (logdev: internal)
XFS (pmem1): bad inode magic/vsn daddr 8723584 #0 (magic=1818)
XFS (pmem1): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x851c80 xfs_inode_buf_verify
XFS (pmem1): Unmount and run xfs_repair
XFS (pmem1): First 128 bytes of corrupted metadata buffer:
00000000: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000010: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000020: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000030: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000040: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000050: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000060: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
00000070: 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 ................
XFS (pmem1): metadata I/O error in "xlog_recover_items_pass2+0x52/0xc0" at daddr 0x851c80 len 32 error 117
XFS (pmem1): log mount/recovery failed: error -117
XFS (pmem1): log mount failed

There have been isolated random other issues, too - xfs_repair fails
because it finds some corruption in symlink blocks, rmap
inconsistencies, etc - but they are nowhere near as common as the
uninitialised inode chunk failure.

The problem has clearly happened at runtime before recovery has run;
I can see the ICREATE log item in the log shortly before the
actively recovered range of the log. This means the ICREATE was
definitely created and written to the log, but for some reason the
tail of the log has been moved past the ordered buffer log item that
tracks INODE_ALLOC buffers and, supposedly, prevents the tail of the
log moving past the ICREATE log item before the inode chunk buffer
is written to disk.

Tracing the fsstress processes that are running when the filesystem
shut down immediately pin-pointed the problem:

user shutdown marks xfs_mount as shutdown

godown-213341 [008] 6398.022871: console: [ 6397.915392] XFS (pmem1): User initiated shutdown received.
.....

aild tries to push ordered inode cluster buffer

xfsaild/pmem1-213314 [001] 6398.022974: xfs_buf_trylock: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 16 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_inode_item_push+0x8e
xfsaild/pmem1-213314 [001] 6398.022976: xfs_ilock_nowait: dev 259:1 ino 0x851c80 flags ILOCK_SHARED caller xfs_iflush_cluster+0xae

xfs_iflush_cluster() checks xfs_is_shutdown(), returns true,
calls xfs_iflush_abort() to kill writeback of the inode.
Inode is removed from AIL, drops cluster buffer reference.

xfsaild/pmem1-213314 [001] 6398.022977: xfs_ail_delete: dev 259:1 lip 0xffff88880247ed80 old lsn 7/20344 new lsn 7/21000 type XFS_LI_INODE flags IN_AIL
xfsaild/pmem1-213314 [001] 6398.022978: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 17 pincount 0 lock 0 flags DONE|INODES|PAGES caller xfs_iflush_abort+0xd7

.....

All inodes on cluster buffer are aborted, then the cluster buffer
itself is aborted and removed from the AIL *without writeback*:

xfsaild/pmem1-213314 [001] 6398.023011: xfs_buf_error_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_ioend_fail+0x33
xfsaild/pmem1-213314 [001] 6398.023012: xfs_ail_delete: dev 259:1 lip 0xffff8888053efde8 old lsn 7/20344 new lsn 7/20344 type XFS_LI_BUF flags IN_AIL

The inode buffer was at 7/20344 when it was removed from the AIL.

xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_item_relse: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_done+0x31
xfsaild/pmem1-213314 [001] 6398.023012: xfs_buf_rele: dev 259:1 daddr 0x851c80 bbcount 0x20 hold 2 pincount 0 lock 0 flags ASYNC|DONE|STALE|INODES|PAGES caller xfs_buf_item_relse+0x39

.....

Userspace is still running, doing stuff. an fsstress process runs
syncfs() or sync() and we end up in sync_fs_one_sb() which issues
a log force. This pushes on the CIL:

fsstress-213322 [001] 6398.024430: xfs_fs_sync_fs: dev 259:1 m_features 0x20000000019ff6e9 opstate (clean|shutdown|inodegc|blockgc) s_flags 0x70810000 caller sync_fs_one_sb+0x26
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x0 caller xfs_fs_sync_fs+0x82
fsstress-213322 [001] 6398.024430: xfs_log_force: dev 259:1 lsn 0x5f caller xfs_log_force+0x7c
<...>-194402 [001] 6398.024467: kmem_alloc: size 176 flags 0x14 caller xlog_cil_push_work+0x9f

And the CIL fills up iclogs with pending changes. This picks up
the current tail from the AIL:

<...>-194402 [001] 6398.024497: xlog_iclog_get_space: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x0 flags caller xlog_write+0x149
<...>-194402 [001] 6398.024498: xlog_iclog_switch: dev 259:1 state XLOG_STATE_ACTIVE refcnt 1 offset 0 lsn 0x700005408 flags caller xlog_state_get_iclog_space+0x37e
<...>-194402 [001] 6398.024521: xlog_iclog_release: dev 259:1 state XLOG_STATE_WANT_SYNC refcnt 1 offset 32256 lsn 0x700005408 flags caller xlog_write+0x5f9
<...>-194402 [001] 6398.024522: xfs_log_assign_tail_lsn: dev 259:1 new tail lsn 7/21000, old lsn 7/20344, last sync 7/21448

And it moves the tail of the log to 7/21000 from 7/20344. This
*moves the tail of the log beyond the ICREATE transaction* that was
at 7/20344 and pinned by the inode cluster buffer that was cancelled
above.

....

godown-213341 [008] 6398.027005: xfs_force_shutdown: dev 259:1 tag logerror flags log_io|force_umount file fs/xfs/xfs_fsops.c line_num 500
godown-213341 [008] 6398.027022: console: [ 6397.915406] pmem1: writeback error on inode 12621949, offset 1019904, sector 12968096
godown-213341 [008] 6398.030551: console: [ 6397.919546] XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/

And finally the log itself is now shutdown, stopping all further
writes to the log. But this is too late to prevent the corruption
that moving the tail of the log forwards after we start cancelling
writeback causes.

The fundamental problem here is that we are using the wrong shutdown
checks for log items. We've long conflated mount shutdown with log
shutdown state, and I started separating that recently with the
atomic shutdown state changes in commit b36d4651e165 ("xfs: make
forced shutdown processing atomic"). The changes in that commit
series are directly responsible for being able to diagnose this
issue because it clearly separated mount shutdown from log shutdown.

Essentially, once we start cancelling writeback of log items and
removing them from the AIL because the filesystem is shut down, we
*cannot* update the journal because we may have cancelled the items
that pin the tail of the log. That moves the tail of the log
forwards without having written the metadata back, hence we have
corrupt in memory state and writing to the journal propagates that
to the on-disk state.

What commit b36d4651e165 makes clear is that log item state needs to
change relative to log shutdown, not mount shutdown. IOWs, anything
that aborts metadata writeback needs to check log shutdown state
because log items directly affect log consistency. Having them check
mount shutdown state introduces the above race condition where we
cancel metadata writeback before the log shuts down.

To fix this, this patch works through all log items and converts
shutdown checks to use xlog_is_shutdown() rather than
xfs_is_shutdown(), so that we don't start aborting metadata
writeback before we shut off journal writes.

AFAICT, this race condition is a zero day IO error handling bug in
XFS that dates back to the introduction of XLOG_IO_ERROR,
XLOG_STATE_IOERROR and XFS_FORCED_SHUTDOWN back in January 1997.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_trans.hdiff 0dc63c8a Thu Feb 22 01:43:36 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: launder in-memory btree buffers before transaction commit

As we've noted in various places, all current users of in-memory btrees
are online fsck. Online fsck only stages a btree long enough to rebuild
an ondisk data structure, which means that the in-memory btree is
ephemeral. Furthermore, if we encounter /any/ errors while updating an
in-memory btree, all we do is tear down all the staged data and return
an errno to userspace. In-memory btrees need not be transactional, so
their buffers should not be committed to the ondisk log, nor should they
be checkpointed by the AIL. That's just as well since the ephemeral
nature of the btree means that the buftarg and the buffers may disappear
quickly anyway.

Therefore, we need a way to launder the btree buffers that get attached
to the transaction by the generic btree code. Because the buffers are
directly mapped to backing file pages, there's no need to bwrite them
back to the tmpfs file. All we need to do is clean enough of the buffer
log item state so that the bli can be detached from the buffer, remove
the bli from the transaction's log item list, and reset the transaction
dirty state as if the laundered items had never been there.

For simplicity, create xfbtree transaction commit and cancel helpers
that launder the in-memory btree buffers for callers. Once laundered,
call the write verifier on non-stale buffers to avoid integrity issues,
or punch a hole in the backing file for stale buffers.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0d227466 Tue May 03 19:50:29 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: intent item whiteouts

When we log modifications based on intents, we add both intent
and intent done items to the modification being made. These get
written to the log to ensure that the operation is re-run if the
intent done is not found in the log.

However, for operations that complete wholly within a single
checkpoint, the change in the checkpoint is atomic and will never
need replay. In this case, we don't need to actually write the
intent and intent done items to the journal because log recovery
will never need to manually restart this modification.

Log recovery currently handles intent/intent done matching by
inserting the intent into the AIL, then removing it when a matching
intent done item is found. Hence for all the intent-based operations
that complete within a checkpoint, we spend all that time parsing
the intent/intent done items just to cancel them and do nothing with
them.

Hence it follows that the only time we actually need intents in the
log is when the modification crosses checkpoint boundaries in the
log and so may only be partially complete in the journal. Hence if
we commit and intent done item to the CIL and the intent item is in
the same checkpoint, we don't actually have to write them to the
journal because log recovery will always cancel the intents.

We've never really worried about the overhead of logging intents
unnecessarily like this because the intents we log are generally
very much smaller than the change being made. e.g. freeing an extent
involves modifying at lease two freespace btree blocks and the AGF,
so the EFI/EFD overhead is only a small increase in space and
processing time compared to the overall cost of freeing an extent.

However, delayed attributes change this cost equation dramatically,
especially for inline attributes. In the case of adding an inline
attribute, we only log the inode core and attribute fork at present.
With delayed attributes, we now log the attr intent which includes
the name and value, the inode core adn attr fork, and finally the
attr intent done item. We increase the number of items we log from 1
to 3, and the number of log vectors (regions) goes up from 3 to 7.
Hence we tripple the number of objects that the CIL has to process,
and more than double the number of log vectors that need to be
written to the journal.

At scale, this means delayed attributes cause a non-pipelined CIL to
become CPU bound processing all the extra items, resulting in a > 40%
performance degradation on 16-way file+xattr create worklaods.
Pipelining the CIL (as per 5.15) reduces the performance degradation
to 20%, but now the limitation is the rate at which the log items
can be written to the iclogs and iclogs be dispatched for IO and
completed.

Even log IO completion is slowed down by these intents, because it
now has to process 3x the number of items in the checkpoint.
Processing completed intents is especially inefficient here, because
we first insert the intent into the AIL, then remove it from the AIL
when the intent done is processed. IOWs, we are also doing expensive
operations in log IO completion we could completely avoid if we
didn't log completed intent/intent done pairs.

Enter log item whiteouts.

When an intent done is committed, we can check to see if the
associated intent is in the same checkpoint as we are currently
committing the intent done to. If so, we can mark the intent log
item with a whiteout and immediately free the intent done item
rather than committing it to the CIL. We can basically skip the
entire formatting and CIL insertion steps for the intent done item.

However, we cannot remove the intent item from the CIL at this point
because the unlocked per-cpu CIL item lists do not permit removal
without holding the CIL context lock exclusively. Transaction commit
only holds the context lock shared, hence the best we can do is mark
the intent item with a whiteout so that the CIL push can release it
rather than writing it to the log.

This means we never write the intent to the log if the intent done
has also been committed to the same checkpoint, but we'll always
write the intent if the intent done has not been committed or has
been committed to a different checkpoint. This will result in
correct log recovery behaviour in all cases, without the overhead of
logging unnecessary intents.

This intent whiteout concept is generic - we can apply it to all
intent/intent done pairs that have a direct 1:1 relationship. The
way deferred ops iterate and relog intents mean that all intents
currently have a 1:1 relationship with their done intent, and hence
we can apply this cancellation to all existing intent/intent done
implementations.

For delayed attributes with a 16-way 64kB xattr create workload,
whiteouts reduce the amount of journalled metadata from ~2.5GB/s
down to ~600MB/s and improve the creation rate from 9000/s to
14000/s.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff b9b3fe15 Wed Apr 20 16:44:59 MDT 2022 Dave Chinner <david@fromorbit.com> xfs: convert buffer flags to unsigned.

5.18 w/ std=gnu11 compiled with gcc-5 wants flags stored in unsigned
fields to be unsigned. This manifests as a compiler error such as:

/kisskb/src/fs/xfs/./xfs_trace.h:432:2: note: in expansion of macro 'TP_printk'
TP_printk("dev %d:%d daddr 0x%llx bbcount 0x%x hold %d pincount %d "
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:5: note: in expansion of macro '__print_flags'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/xfs_buf.h:67:4: note: in expansion of macro 'XBF_UNMAPPED'
{ XBF_UNMAPPED, "UNMAPPED" }
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:40: note: in expansion of macro 'XFS_BUF_FLAGS'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/./xfs_trace.h: In function 'trace_raw_output_xfs_buf_flags_class':
/kisskb/src/fs/xfs/xfs_buf.h:46:23: error: initializer element is not constant
#define XBF_UNMAPPED (1 << 31)/* do not map the buffer */

as __print_flags assigns XFS_BUF_FLAGS to a structure that uses an
unsigned long for the flag. Since this results in the value of
XBF_UNMAPPED causing a signed integer overflow, the result is
technically undefined behavior, which gcc-5 does not accept as an
integer constant.

This is based on a patch from Arnd Bergman <arnd@arndb.de>.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff b9b3fe15 Wed Apr 20 16:44:59 MDT 2022 Dave Chinner <david@fromorbit.com> xfs: convert buffer flags to unsigned.

5.18 w/ std=gnu11 compiled with gcc-5 wants flags stored in unsigned
fields to be unsigned. This manifests as a compiler error such as:

/kisskb/src/fs/xfs/./xfs_trace.h:432:2: note: in expansion of macro 'TP_printk'
TP_printk("dev %d:%d daddr 0x%llx bbcount 0x%x hold %d pincount %d "
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:5: note: in expansion of macro '__print_flags'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/xfs_buf.h:67:4: note: in expansion of macro 'XBF_UNMAPPED'
{ XBF_UNMAPPED, "UNMAPPED" }
^
/kisskb/src/fs/xfs/./xfs_trace.h:440:40: note: in expansion of macro 'XFS_BUF_FLAGS'
__print_flags(__entry->flags, "|", XFS_BUF_FLAGS),
^
/kisskb/src/fs/xfs/./xfs_trace.h: In function 'trace_raw_output_xfs_buf_flags_class':
/kisskb/src/fs/xfs/xfs_buf.h:46:23: error: initializer element is not constant
#define XBF_UNMAPPED (1 << 31)/* do not map the buffer */

as __print_flags assigns XFS_BUF_FLAGS to a structure that uses an
unsigned long for the flag. Since this results in the value of
XBF_UNMAPPED causing a signed integer overflow, the result is
technically undefined behavior, which gcc-5 does not accept as an
integer constant.

This is based on a patch from Arnd Bergman <arnd@arndb.de>.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 1aec7c3d Fri Apr 23 17:02:00 MDT 2021 Darrick J. Wong <djwong@kernel.org> xfs: remove obsolete AGF counter debugging

In commit f8f2835a9cf3 we changed the behavior of XFS to use EFIs to
remove blocks from an overfilled AGFL because there were complaints
about transaction overruns that stemmed from trying to free multiple
blocks in a single transaction.

Unfortunately, that commit missed a subtlety in the debug-mode
transaction accounting when a realtime volume is attached. If a
realtime file undergoes a data fork mapping change such that realtime
extents are allocated (or freed) in the same transaction that a data
device block is also allocated (or freed), we can trip a debugging
assertion. This can happen (for example) if a realtime extent is
allocated and it is necessary to reshape the bmbt to hold the new
mapping.

When we go to allocate a bmbt block from an AG, the first thing the data
device block allocator does is ensure that the freelist is the proper
length. If the freelist is too long, it will trim the freelist to the
proper length.

In debug mode, trimming the freelist calls xfs_trans_agflist_delta() to
record the decrement in the AG free list count. Prior to f8f28 we would
put the free block back in the free space btrees in the same
transaction, which calls xfs_trans_agblocks_delta() to record the
increment in the AG free block count. Since AGFL blocks are included in
the global free block count (fdblocks), there is no corresponding
fdblocks update, so the AGFL free satisfies the following condition in
xfs_trans_apply_sb_deltas:

/*
* Check that superblock mods match the mods made to AGF counters.
*/
ASSERT((tp->t_fdblocks_delta + tp->t_res_fdblocks_delta) ==
(tp->t_ag_freeblks_delta + tp->t_ag_flist_delta +
tp->t_ag_btree_delta));

The comparison here used to be: (X + 0) == ((X+1) + -1 + 0), where X is
the number blocks that were allocated.

After commit f8f28 we defer the block freeing to the next chained
transaction, which means that the calls to xfs_trans_agflist_delta and
xfs_trans_agblocks_delta occur in separate transactions. The (first)
transaction that shortens the free list trips on the comparison, which
has now become:

(X + 0) == ((X) + -1 + 0)

because we haven't freed the AGFL block yet; we've only logged an
intention to free it. When the second transaction (the deferred free)
commits, it will evaluate the expression as:

(0 + 0) == (1 + 0 + 0)

and trip over that in turn.

At this point, the astute reader may note that the two commits tagged by
this patch have been in the kernel for a long time but haven't generated
any bug reports. How is it that the author became aware of this bug?

This originally surfaced as an intermittent failure when I was testing
realtime rmap, but a different bug report by Zorro Lang reveals the same
assertion occuring on !lazysbcount filesystems.

The common factor to both reports (and why this problem wasn't
previously reported) becomes apparent if we consider when
xfs_trans_apply_sb_deltas is called by __xfs_trans_commit():

if (tp->t_flags & XFS_TRANS_SB_DIRTY)
xfs_trans_apply_sb_deltas(tp);

With a modern lazysbcount filesystem, transactions update only the
percpu counters, so they don't need to set XFS_TRANS_SB_DIRTY, hence
xfs_trans_apply_sb_deltas is rarely called.

However, updates to the count of free realtime extents are not part of
lazysbcount, so XFS_TRANS_SB_DIRTY will be set on transactions adding or
removing data fork mappings to realtime files; similarly,
XFS_TRANS_SB_DIRTY is always set on !lazysbcount filesystems.

Dave mentioned in response to an earlier version of this patch:

"IIUC, what you are saying is that this debug code is simply not
exercised in normal testing and hasn't been for the past decade? And it
still won't be exercised on anything other than realtime device testing?

"...it was debugging code from 1994 that was largely turned into dead
code when lazysbcounters were introduced in 2007. Hence I'm not sure it
holds any value anymore."

This debugging code isn't especially helpful - you can modify the
flcount on one AG and the freeblks of another AG, and it won't trigger.
Add the fact that nobody noticed for a decade, and let's just get rid of
it (and start testing realtime :P).

This bug was found by running generic/051 on either a V4 filesystem
lacking lazysbcount; or a V5 filesystem with a realtime volume.

Cc: bfoster@redhat.com, zlang@redhat.com
Fixes: f8f2835a9cf3 ("xfs: defer agfl block frees when dfops is available")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
H A Dxfs_icache.cdiff f12b9668 Mon Sep 11 09:39:07 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: use i_prev_unlinked to distinguish inodes that are not on the unlinked list

Alter the definition of i_prev_unlinked slightly to make it more obvious
when an inode with 0 link count is not part of the iunlink bucket lists
rooted in the AGI. This distinction is necessary because it is not
sufficient to check inode.i_nlink to decide if an inode is on the
unlinked list. Updates to i_nlink can happen while holding only
ILOCK_EXCL, but updates to an inode's position in the AGI unlinked list
(which happen after the nlink update) requires both ILOCK_EXCL and the
AGI buffer lock.

The next few patches will make it possible to reload an entire unlinked
bucket list when we're walking the inode table or performing handle
operations and need more than the ability to iget the last inode in the
chain.

The upcoming directory repair code also needs to be able to make this
distinction to decide if a zero link count directory should be moved to
the orphanage or allowed to inactivate. An upcoming enhancement to the
online AGI fsck code will need this distinction to check and rebuild the
AGI unlinked buckets.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0d296634 Thu Aug 10 08:48:12 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: hide xfs_inode_is_allocated in scrub common code

This function is only used by online fsck, so let's move it there.
In the next patch, we'll fix it to work properly and to require that the
caller hold the AGI buffer locked. No major changes aside from
adjusting the signature a bit.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 2254a739 Mon May 01 17:16:14 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: fix xfs_inodegc_stop racing with mod_delayed_work

syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

This warning corresponds to this code in __queue_work:

/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;

For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:

Thread 0 Thread 1 Thread 2

xfs_inodegc_stop

xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>

xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>

xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>

drain_workqueue
<set WQ_DRAINING>

llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>

In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.

We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.

There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).

There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.

Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.

Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
H A Dxfs_aops.cdiff 4ce02c67 Mon Jul 10 15:12:43 MDT 2023 Ritesh Harjani (IBM) <ritesh.list@gmail.com> iomap: Add per-block dirty state tracking to improve performance

When filesystem blocksize is less than folio size (either with
mapping_large_folio_support() or with blocksize < pagesize) and when the
folio is uptodate in pagecache, then even a byte write can cause
an entire folio to be written to disk during writeback. This happens
because we currently don't have a mechanism to track per-block dirty
state within struct iomap_folio_state. We currently only track uptodate
state.

This patch implements support for tracking per-block dirty state in
iomap_folio_state->state bitmap. This should help improve the filesystem
write performance and help reduce write amplification.

Performance testing of below fio workload reveals ~16x performance
improvement using nvme with XFS (4k blocksize) on Power (64K pagesize)
FIO reported write bw scores improved from around ~28 MBps to ~452 MBps.

1. <test_randwrite.fio>
[global]
ioengine=psync
rw=randwrite
overwrite=1
pre_read=1
direct=0
bs=4k
size=1G
dir=./
numjobs=8
fdatasync=1
runtime=60
iodepth=64
group_reporting=1

[fio-run]

2. Also our internal performance team reported that this patch improves
their database workload performance by around ~83% (with XFS on Power)

Reported-by: Aravinda Herle <araherle@in.ibm.com>
Reported-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
diff 8ac5b996 Sun Mar 05 16:13:23 MST 2023 Dave Chinner <dchinner@redhat.com> xfs: fix off-by-one-block in xfs_discard_folio()

The recent writeback corruption fixes changed the code in
xfs_discard_folio() to calculate a byte range to for punching
delalloc extents. A mistake was made in using round_up(pos) for the
end offset, because when pos points at the first byte of a block, it
does not get rounded up to point to the end byte of the block. hence
the punch range is short, and this leads to unexpected behaviour in
certain cases in xfs_bmap_punch_delalloc_range.

e.g. pos = 0 means we call xfs_bmap_punch_delalloc_range(0,0), so
there is no previous extent and it rounds up the punch to the end of
the delalloc extent it found at offset 0, not the end of the range
given to xfs_bmap_punch_delalloc_range().

Fix this by handling the zero block offset case correctly.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217030
Link: https://lore.kernel.org/linux-xfs/Y+vOfaxIWX1c%2Fyy9@bfoster/
Fixes: 7348b322332d ("xfs: xfs_bmap_punch_delalloc_range() should take a byte range")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Found-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 8ac5b996 Sun Mar 05 16:13:23 MST 2023 Dave Chinner <dchinner@redhat.com> xfs: fix off-by-one-block in xfs_discard_folio()

The recent writeback corruption fixes changed the code in
xfs_discard_folio() to calculate a byte range to for punching
delalloc extents. A mistake was made in using round_up(pos) for the
end offset, because when pos points at the first byte of a block, it
does not get rounded up to point to the end byte of the block. hence
the punch range is short, and this leads to unexpected behaviour in
certain cases in xfs_bmap_punch_delalloc_range.

e.g. pos = 0 means we call xfs_bmap_punch_delalloc_range(0,0), so
there is no previous extent and it rounds up the punch to the end of
the delalloc extent it found at offset 0, not the end of the range
given to xfs_bmap_punch_delalloc_range().

Fix this by handling the zero block offset case correctly.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217030
Link: https://lore.kernel.org/linux-xfs/Y+vOfaxIWX1c%2Fyy9@bfoster/
Fixes: 7348b322332d ("xfs: xfs_bmap_punch_delalloc_range() should take a byte range")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Found-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 8ac5b996 Sun Mar 05 16:13:23 MST 2023 Dave Chinner <dchinner@redhat.com> xfs: fix off-by-one-block in xfs_discard_folio()

The recent writeback corruption fixes changed the code in
xfs_discard_folio() to calculate a byte range to for punching
delalloc extents. A mistake was made in using round_up(pos) for the
end offset, because when pos points at the first byte of a block, it
does not get rounded up to point to the end byte of the block. hence
the punch range is short, and this leads to unexpected behaviour in
certain cases in xfs_bmap_punch_delalloc_range.

e.g. pos = 0 means we call xfs_bmap_punch_delalloc_range(0,0), so
there is no previous extent and it rounds up the punch to the end of
the delalloc extent it found at offset 0, not the end of the range
given to xfs_bmap_punch_delalloc_range().

Fix this by handling the zero block offset case correctly.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217030
Link: https://lore.kernel.org/linux-xfs/Y+vOfaxIWX1c%2Fyy9@bfoster/
Fixes: 7348b322332d ("xfs: xfs_bmap_punch_delalloc_range() should take a byte range")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Found-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 8ac5b996 Sun Mar 05 16:13:23 MST 2023 Dave Chinner <dchinner@redhat.com> xfs: fix off-by-one-block in xfs_discard_folio()

The recent writeback corruption fixes changed the code in
xfs_discard_folio() to calculate a byte range to for punching
delalloc extents. A mistake was made in using round_up(pos) for the
end offset, because when pos points at the first byte of a block, it
does not get rounded up to point to the end byte of the block. hence
the punch range is short, and this leads to unexpected behaviour in
certain cases in xfs_bmap_punch_delalloc_range.

e.g. pos = 0 means we call xfs_bmap_punch_delalloc_range(0,0), so
there is no previous extent and it rounds up the punch to the end of
the delalloc extent it found at offset 0, not the end of the range
given to xfs_bmap_punch_delalloc_range().

Fix this by handling the zero block offset case correctly.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217030
Link: https://lore.kernel.org/linux-xfs/Y+vOfaxIWX1c%2Fyy9@bfoster/
Fixes: 7348b322332d ("xfs: xfs_bmap_punch_delalloc_range() should take a byte range")
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Found-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff ebb7fb15 Wed Jan 26 10:19:20 MST 2022 Dave Chinner <dchinner@redhat.com> xfs, iomap: limit individual ioend chain lengths in writeback

Trond Myklebust reported soft lockups in XFS IO completion such as
this:

watchdog: BUG: soft lockup - CPU#12 stuck for 23s! [kworker/12:1:3106]
CPU: 12 PID: 3106 Comm: kworker/12:1 Not tainted 4.18.0-305.10.2.el8_4.x86_64 #1
Workqueue: xfs-conv/md127 xfs_end_io [xfs]
RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x20
Call Trace:
wake_up_page_bit+0x8a/0x110
iomap_finish_ioend+0xd7/0x1c0
iomap_finish_ioends+0x7f/0xb0
xfs_end_ioend+0x6b/0x100 [xfs]
xfs_end_io+0xb9/0xe0 [xfs]
process_one_work+0x1a7/0x360
worker_thread+0x1fa/0x390
kthread+0x116/0x130
ret_from_fork+0x35/0x40

Ioends are processed as an atomic completion unit when all the
chained bios in the ioend have completed their IO. Logically
contiguous ioends can also be merged and completed as a single,
larger unit. Both of these things can be problematic as both the
bio chains per ioend and the size of the merged ioends processed as
a single completion are both unbound.

If we have a large sequential dirty region in the page cache,
write_cache_pages() will keep feeding us sequential pages and we
will keep mapping them into ioends and bios until we get a dirty
page at a non-sequential file offset. These large sequential runs
can will result in bio and ioend chaining to optimise the io
patterns. The pages iunder writeback are pinned within these chains
until the submission chaining is broken, allowing the entire chain
to be completed. This can result in huge chains being processed
in IO completion context.

We get deep bio chaining if we have large contiguous physical
extents. We will keep adding pages to the current bio until it is
full, then we'll chain a new bio to keep adding pages for writeback.
Hence we can build bio chains that map millions of pages and tens of
gigabytes of RAM if the page cache contains big enough contiguous
dirty file regions. This long bio chain pins those pages until the
final bio in the chain completes and the ioend can iterate all the
chained bios and complete them.

OTOH, if we have a physically fragmented file, we end up submitting
one ioend per physical fragment that each have a small bio or bio
chain attached to them. We do not chain these at IO submission time,
but instead we chain them at completion time based on file
offset via iomap_ioend_try_merge(). Hence we can end up with unbound
ioend chains being built via completion merging.

XFS can then do COW remapping or unwritten extent conversion on that
merged chain, which involves walking an extent fragment at a time
and running a transaction to modify the physical extent information.
IOWs, we merge all the discontiguous ioends together into a
contiguous file range, only to then process them individually as
discontiguous extents.

This extent manipulation is computationally expensive and can run in
a tight loop, so merging logically contiguous but physically
discontigous ioends gains us nothing except for hiding the fact the
fact we broke the ioends up into individual physical extents at
submission and then need to loop over those individual physical
extents at completion.

Hence we need to have mechanisms to limit ioend sizes and
to break up completion processing of large merged ioend chains:

1. bio chains per ioend need to be bound in length. Pure overwrites
go straight to iomap_finish_ioend() in softirq context with the
exact bio chain attached to the ioend by submission. Hence the only
way to prevent long holdoffs here is to bound ioend submission
sizes because we can't reschedule in softirq context.

2. iomap_finish_ioends() has to handle unbound merged ioend chains
correctly. This relies on any one call to iomap_finish_ioend() being
bound in runtime so that cond_resched() can be issued regularly as
the long ioend chain is processed. i.e. this relies on mechanism #1
to limit individual ioend sizes to work correctly.

3. filesystems have to loop over the merged ioends to process
physical extent manipulations. This means they can loop internally,
and so we break merging at physical extent boundaries so the
filesystem can easily insert reschedule points between individual
extent manipulations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-and-tested-by: Trond Myklebust <trondmy@hammerspace.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_trace.hdiff 0dc63c8a Thu Feb 22 01:43:36 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: launder in-memory btree buffers before transaction commit

As we've noted in various places, all current users of in-memory btrees
are online fsck. Online fsck only stages a btree long enough to rebuild
an ondisk data structure, which means that the in-memory btree is
ephemeral. Furthermore, if we encounter /any/ errors while updating an
in-memory btree, all we do is tear down all the staged data and return
an errno to userspace. In-memory btrees need not be transactional, so
their buffers should not be committed to the ondisk log, nor should they
be checkpointed by the AIL. That's just as well since the ephemeral
nature of the btree means that the buftarg and the buffers may disappear
quickly anyway.

Therefore, we need a way to launder the btree buffers that get attached
to the transaction by the generic btree code. Because the buffers are
directly mapped to backing file pages, there's no need to bwrite them
back to the tmpfs file. All we need to do is clean enough of the buffer
log item state so that the bli can be detached from the buffer, remove
the bli from the transaction's log item list, and reset the transaction
dirty state as if the laundered items had never been there.

For simplicity, create xfbtree transaction commit and cancel helpers
that launder the in-memory btree buffers for callers. Once laundered,
call the write verifier on non-stale buffers to avoid integrity issues,
or punch a hole in the backing file for stale buffers.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0e24ec3c Thu Feb 22 01:33:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remember sick inodes that get inactivated

If an unhealthy inode gets inactivated, remember this fact in the
per-fs health summary.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0b8686f1 Thu Feb 22 01:31:01 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: separate the marking of sick and checked metadata

Split the setting of the sick and checked masks into separate functions
as part of preparing to add the ability for regular runtime fs code
(i.e. not scrub) to mark metadata structures sick when corruptions are
found. Improve the documentation of libxfs' requirements for helper
behavior.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 68b957f6 Mon Sep 11 09:39:06 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: load uncached unlinked inodes into memory on demand

shrikanth hegde reports that filesystems fail shortly after mount with
the following failure:

WARNING: CPU: 56 PID: 12450 at fs/xfs/xfs_inode.c:1839 xfs_iunlink_lookup+0x58/0x80 [xfs]

This of course is the WARN_ON_ONCE in xfs_iunlink_lookup:

ip = radix_tree_lookup(&pag->pag_ici_root, agino);
if (WARN_ON_ONCE(!ip || !ip->i_ino)) { ... }

From diagnostic data collected by the bug reporters, it would appear
that we cleanly mounted a filesystem that contained unlinked inodes.
Unlinked inodes are only processed as a final step of log recovery,
which means that clean mounts do not process the unlinked list at all.

Prior to the introduction of the incore unlinked lists, this wasn't a
problem because the unlink code would (very expensively) traverse the
entire ondisk metadata iunlink chain to keep things up to date.
However, the incore unlinked list code complains when it realizes that
it is out of sync with the ondisk metadata and shuts down the fs, which
is bad.

Ritesh proposed to solve this problem by unconditionally parsing the
unlinked lists at mount time, but this imposes a mount time cost for
every filesystem to catch something that should be very infrequent.
Instead, let's target the places where we can encounter a next_unlinked
pointer that refers to an inode that is not in cache, and load it into
cache.

Note: This patch does not address the problem of iget loading an inode
from the middle of the iunlink list and needing to set i_prev_unlinked
correctly.

Reported-by: shrikanth hegde <sshegde@linux.vnet.ibm.com>
Triaged-by: Ritesh Harjani <ritesh.list@gmail.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 68b957f6 Mon Sep 11 09:39:06 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: load uncached unlinked inodes into memory on demand

shrikanth hegde reports that filesystems fail shortly after mount with
the following failure:

WARNING: CPU: 56 PID: 12450 at fs/xfs/xfs_inode.c:1839 xfs_iunlink_lookup+0x58/0x80 [xfs]

This of course is the WARN_ON_ONCE in xfs_iunlink_lookup:

ip = radix_tree_lookup(&pag->pag_ici_root, agino);
if (WARN_ON_ONCE(!ip || !ip->i_ino)) { ... }

From diagnostic data collected by the bug reporters, it would appear
that we cleanly mounted a filesystem that contained unlinked inodes.
Unlinked inodes are only processed as a final step of log recovery,
which means that clean mounts do not process the unlinked list at all.

Prior to the introduction of the incore unlinked lists, this wasn't a
problem because the unlink code would (very expensively) traverse the
entire ondisk metadata iunlink chain to keep things up to date.
However, the incore unlinked list code complains when it realizes that
it is out of sync with the ondisk metadata and shuts down the fs, which
is bad.

Ritesh proposed to solve this problem by unconditionally parsing the
unlinked lists at mount time, but this imposes a mount time cost for
every filesystem to catch something that should be very infrequent.
Instead, let's target the places where we can encounter a next_unlinked
pointer that refers to an inode that is not in cache, and load it into
cache.

Note: This patch does not address the problem of iget loading an inode
from the middle of the iunlink list and needing to set i_prev_unlinked
correctly.

Reported-by: shrikanth hegde <sshegde@linux.vnet.ibm.com>
Triaged-by: Ritesh Harjani <ritesh.list@gmail.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff f045dd00 Thu Jun 29 18:39:44 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: clean up the rtbitmap fsmap backend

The rtbitmap fsmap backend doesn't query the rmapbt, so it's wasteful to
spend time initializing the rmap_irec objects. Worse yet, the logic to
query the rtbitmap is spread across three separate functions, which is
unnecessarily difficult to follow.

Compute the start rtextent that we want from keys[0] directly and
combine the functions to avoid passing parameters around everywhere, and
consolidate all the logic into a single function. At one point many
years ago I intended to use __xfs_getfsmap_rtdev as the launching point
for realtime rmapbt queries, but this hasn't been the case for a long
time.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 0b11553e Wed Feb 01 11:16:04 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: pass refcount intent directly through the log intent code

Pass the incore refcount intent through the CUI logging code instead of
repeatedly boxing and unboxing parameters.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff 8838dafe Sun Sep 18 14:51:14 MDT 2022 Zeng Heng <zengheng4@huawei.com> xfs: missing space in xfs trace log

Add space between arguments would help someone
to locate the key words they want, so break
quoted strings at a space character.

Such as below:
[Before]
kworker/1:0-280 [001] ..... 600.782135: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffffflags ATTRFORK ...

[After]
kworker/1:2-564 [001] ..... 23817.906160: xfs_bunmap:
dev 7:0 ino 0x85 disize 0x0 fileoff 0x0 fsbcount 0x400000001fffff flags ATTRFORK ...

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
H A Dxfs_dquot.cdiff 0c6ca06a Thu Mar 14 07:16:39 MDT 2024 Dave Chinner <dchinner@redhat.com> xfs: quota radix tree allocations need to be NOFS on insert

In converting the XFS code from GFP_NOFS to scoped contexts, we
converted the quota radix tree to GFP_KERNEL. Unfortunately, it was
not clearly documented that this set was because there is a
dependency on the quotainfo->qi_tree_lock being taken in memory
reclaim to remove dquots from the radix tree.

In hindsight this is obvious, but the radix tree allocations on
insert are not immediately obvious, and we avoid this for the inode
cache radix trees by using preloading and hence completely avoiding
the radix tree node allocation under tree lock constraints.

Hence there are a few solutions here. The first is to reinstate
GFP_NOFS for the radix tree and add a comment explaining why
GFP_NOFS is used. The second is to use memalloc_nofs_save() on the
radix tree insert context, which makes it obvious that the radix
tree insert runs under GFP_NOFS constraints. The third option is to
simply replace the radix tree and it's lock with an xarray which can
do memory allocation safely in an insert context.

The first is OK, but not really the direction we want to head. The
second is my preferred short term solution. The third - converting
XFS radix trees to xarray - is the longer term solution.

Hence to fix the regression here, we take option 2 as it moves us in
the direction we want to head with memory allocation and GFP_NOFS
removal.

Reported-by: syzbot+8fdff861a781522bda4d@syzkaller.appspotmail.com
Reported-by: syzbot+d247769793ec169e4bf9@syzkaller.appspotmail.com
Fixes: 94a69db2367e ("xfs: use __GFP_NOLOCKDEP instead of GFP_NOFS")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 0a97c01c Thu Nov 30 12:40:18 MST 2023 Nhat Pham <nphamcs@gmail.com> list_lru: allow explicit memcg and NUMA node selection

Patch series "workload-specific and memory pressure-driven zswap
writeback", v8.

There are currently several issues with zswap writeback:

1. There is only a single global LRU for zswap, making it impossible to
perform worload-specific shrinking - an memcg under memory pressure
cannot determine which pages in the pool it owns, and often ends up
writing pages from other memcgs. This issue has been previously
observed in practice and mitigated by simply disabling
memcg-initiated shrinking:

https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@gmail.com/T/#u

But this solution leaves a lot to be desired, as we still do not
have an avenue for an memcg to free up its own memory locked up in
the zswap pool.

2. We only shrink the zswap pool when the user-defined limit is hit.
This means that if we set the limit too high, cold data that are
unlikely to be used again will reside in the pool, wasting precious
memory. It is hard to predict how much zswap space will be needed
ahead of time, as this depends on the workload (specifically, on
factors such as memory access patterns and compressibility of the
memory pages).

This patch series solves these issues by separating the global zswap LRU
into per-memcg and per-NUMA LRUs, and performs workload-specific (i.e
memcg- and NUMA-aware) zswap writeback under memory pressure. The new
shrinker does not have any parameter that must be tuned by the user, and
can be opted in or out on a per-memcg basis.

As a proof of concept, we ran the following synthetic benchmark: build the
linux kernel in a memory-limited cgroup, and allocate some cold data in
tmpfs to see if the shrinker could write them out and improved the overall
performance. Depending on the amount of cold data generated, we observe
from 14% to 35% reduction in kernel CPU time used in the kernel builds.


This patch (of 6):

The interface of list_lru is based on the assumption that the list node
and the data it represents belong to the same allocated on the correct
node/memcg. While this assumption is valid for existing slab objects LRU
such as dentries and inodes, it is undocumented, and rather inflexible for
certain potential list_lru users (such as the upcoming zswap shrinker and
the THP shrinker). It has caused us a lot of issues during our
development.

This patch changes list_lru interface so that the caller must explicitly
specify numa node and memcg when adding and removing objects. The old
list_lru_add() and list_lru_del() are renamed to list_lru_add_obj() and
list_lru_del_obj(), respectively.

It also extends the list_lru API with a new function, list_lru_putback,
which undoes a previous list_lru_isolate call. Unlike list_lru_add, it
does not increment the LRU node count (as list_lru_isolate does not
decrement the node count). list_lru_putback also allows for explicit
memcg and NUMA node selection.

Link: https://lkml.kernel.org/r/20231130194023.4102148-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-2-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff 0b04dd5d Wed Jul 15 18:51:47 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: always use xfs_dquot_type when extracting type from a dquot

Always use the xfs_dquot_type helper to extract the quota type from an
incore dquot. This moves responsibility for filtering internal state
information and whatnot to anybody passing around a struct xfs_dquot.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0b0fa1d1 Tue Jul 14 11:37:22 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: stop using q_core.d_flags in the quota code

Use the incore dq_flags to figure out the dquot type. This is the first
step towards removing xfs_disk_dquot from the incore dquot.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
diff 0c7e5afb Mon Jun 29 15:48:46 MDT 2020 Dave Chinner <david@fromorbit.com> xfs: mark dquot buffers in cache

dquot buffers always have write IO callbacks, so by marking them
directly we can avoid needing to attach ->b_iodone functions to
them. This avoids an indirect call, and makes future modifications
much simpler.

This is largely a rearrangement of the code at this point - no IO
completion functionality changes at this point, just how the
code is run is modified.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 78bba5c8 Wed May 13 16:33:27 MDT 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: use ordered buffers to initialize dquot buffers during quotacheck

While QAing the new xfs_repair quotacheck code, I uncovered a quota
corruption bug resulting from a bad interaction between dquot buffer
initialization and quotacheck. The bug can be reproduced with the
following sequence:

# mkfs.xfs -f /dev/sdf
# mount /dev/sdf /opt -o usrquota
# su nobody -s /bin/bash -c 'touch /opt/barf'
# sync
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
nobody 1 0 0 00 [------]

# xfs_io -x -c 'shutdown' /opt
# umount /opt
# mount /dev/sdf /opt -o usrquota
# touch /opt/man2
# xfs_quota -x -c 'report -ahi' /opt
User quota on /opt (/dev/sdf)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 1 0 0 00 [------]
nobody 1 0 0 00 [------]

# umount /opt

Notice how the initial quotacheck set the root dquot icount to 3
(rootino, rbmino, rsumino), but after shutdown -> remount -> recovery,
xfs_quota reports that the root dquot has only 1 icount. We haven't
deleted anything from the filesystem, which means that quota is now
under-counting. This behavior is not limited to icount or the root
dquot, but this is the shortest reproducer.

I traced the cause of this discrepancy to the way that we handle ondisk
dquot updates during quotacheck vs. regular fs activity. Normally, when
we allocate a disk block for a dquot, we log the buffer as a regular
(dquot) buffer. Subsequent updates to the dquots backed by that block
are done via separate dquot log item updates, which means that they
depend on the logged buffer update being written to disk before the
dquot items. Because individual dquots have their own LSN fields, that
initial dquot buffer must always be recovered.

However, the story changes for quotacheck, which can cause dquot block
allocations but persists the final dquot counter values via a delwri
list. Because recovery doesn't gate dquot buffer replay on an LSN, this
means that the initial dquot buffer can be replayed over the (newer)
contents that were delwritten at the end of quotacheck. In effect, this
re-initializes the dquot counters after they've been updated. If the
log does not contain any other dquot items to recover, the obsolete
dquot contents will not be corrected by log recovery.

Because quotacheck uses a transaction to log the setting of the CHKD
flags in the superblock, we skip quotacheck during the second mount
call, which allows the incorrect icount to remain.

Fix this by changing the ondisk dquot initialization function to use
ordered buffers to write out fresh dquot blocks if it detects that we're
running quotacheck. If the system goes down before quotacheck can
complete, the CHKD flags will not be set in the superblock and the next
mount will run quotacheck again, which can fix uninitialized dquot
buffers. This requires amending the defer code to maintaine ordered
buffer state across defer rolls for the sake of the dquot allocation
code.

For regular operations we preserve the current behavior since the dquot
items require properly initialized ondisk dquot records.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
H A Dxfs_trans_dquot.cdiff 707e0dda Mon Aug 26 01:06:22 MDT 2019 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> fs: xfs: Remove KM_NOSLEEP and KM_SLEEP.

Since no caller is using KM_NOSLEEP and no callee branches on KM_SLEEP,
we can remove KM_NOSLEEP and replace KM_SLEEP with 0.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_trans_ail.cdiff 939bd50d Wed Jun 28 12:04:31 MDT 2023 Dave Chinner <dchinner@redhat.com> xfs: don't reverse order of items in bulk AIL insertion

XFS has strict metadata ordering requirements. One of the things it
does is maintain the commit order of items from transaction commit
through the CIL and into the AIL. That is, if a transaction logs
item A before item B in a modification, then they will be inserted
into the CIL in the order {A, B}. These items are then written into
the iclog during checkpointing in the order {A, B}. When the
checkpoint commits, they are supposed to be inserted into the AIL in
the order {A, B}, and when they are pushed from the AIL, they are
pushed in the order {A, B}.

If we crash, log recovery then replays the two items from the
checkpoint in the order {A, B}, resulting in the objects the items
apply to being queued for writeback at the end of the checkpoint
in the order {A, B}. This means recovery behaves the same way as the
runtime code.

In places, we have subtle dependencies on this ordering being
maintained. One of this place is performing intent recovery from the
log. It assumes that recovering an intent will result in a
non-intent object being the first thing that is modified in the
recovery transaction, and so when the transaction commits and the
journal flushes, the first object inserted into the AIL beyond the
intent recovery range will be a non-intent item. It uses the
transistion from intent items to non-intent items to stop the
recovery pass.

A recent log recovery issue indicated that an intent was appearing
as the first item in the AIL beyond the recovery range, hence
breaking the end of recovery detection that exists.

Tracing indicated insertion of the items into the AIL was apparently
occurring in the right order (the intent was last in the commit item
list), but the intent was appearing first in the AIL. IOWs, the
order of items in the AIL was {D,C,B,A}, not {A,B,C,D}, and bulk
insertion was reversing the order of the items in the batch of items
being inserted.

Lucky for us, all the items fed to bulk insertion have the same LSN,
so the reversal of order does not affect the log head/tail tracking
that is based on the contents of the AIL. It only impacts on code
that has implicit, subtle dependencies on object order, and AFAICT
only the intent recovery loop is impacted by it.

Make sure bulk AIL insertion does not reorder items incorrectly.

Fixes: 0e57f6a36f9b ("xfs: bulk AIL insertion during transaction commit")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_trans_buf.cdiff 0dc63c8a Thu Feb 22 01:43:36 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: launder in-memory btree buffers before transaction commit

As we've noted in various places, all current users of in-memory btrees
are online fsck. Online fsck only stages a btree long enough to rebuild
an ondisk data structure, which means that the in-memory btree is
ephemeral. Furthermore, if we encounter /any/ errors while updating an
in-memory btree, all we do is tear down all the staged data and return
an errno to userspace. In-memory btrees need not be transactional, so
their buffers should not be committed to the ondisk log, nor should they
be checkpointed by the AIL. That's just as well since the ephemeral
nature of the btree means that the buftarg and the buffers may disappear
quickly anyway.

Therefore, we need a way to launder the btree buffers that get attached
to the transaction by the generic btree code. Because the buffers are
directly mapped to backing file pages, there's no need to bwrite them
back to the tmpfs file. All we need to do is clean enough of the buffer
log item state so that the bli can be detached from the buffer, remove
the bli from the transaction's log item list, and reset the transaction
dirty state as if the laundered items had never been there.

For simplicity, create xfbtree transaction commit and cancel helpers
that launder the in-memory btree buffers for callers. Once laundered,
call the write verifier on non-stale buffers to avoid integrity issues,
or punch a hole in the backing file for stale buffers.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 04fcad80 Wed Aug 18 19:46:57 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: introduce xfs_buf_daddr()

Introduce a helper function xfs_buf_daddr() to extract the disk
address of the buffer from the struct xfs_buf. This will replace
direct accesses to bp->b_bn and bp->b_maps[0].bm_bn, as well as
the XFS_BUF_ADDR() macro.

This patch introduces the helper function and replaces all uses of
XFS_BUF_ADDR() as this is just a simple sed replacement.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0c7e5afb Mon Jun 29 15:48:46 MDT 2020 Dave Chinner <david@fromorbit.com> xfs: mark dquot buffers in cache

dquot buffers always have write IO callbacks, so by marking them
directly we can avoid needing to attach ->b_iodone functions to
them. This avoids an indirect call, and makes future modifications
much simpler.

This is largely a rearrangement of the code at this point - no IO
completion functionality changes at this point, just how the
code is run is modified.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 8c9ce2f7 Wed Jun 12 09:59:58 MDT 2019 Eric Sandeen <sandeen@sandeen.net> xfs: remove unused flags arg from getsb interfaces

The flags value is always passed as 0 so remove the argument.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_trans.cdiff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 3c4cb76b Tue Mar 29 19:22:01 MDT 2022 Dave Chinner <dchinner@redhat.com> xfs: xfs_trans_commit() path must check for log shutdown

If a shut races with xfs_trans_commit() and we have shut down the
filesystem but not the log, we will still cancel the transaction.
This can result in aborting dirty log items instead of committing and
pinning them whilst the log is still running. Hence we can end up
with dirty, unlogged metadata that isn't in the AIL in memory that
can be flushed to disk via writeback clustering.

This was discovered from a g/388 trace where an inode log item was
having IO completed on it and it wasn't in the AIL, hence tripping
asserts xfs_ail_check(). Inode cluster writeback started long after
the filesystem shutdown started, and long after the transaction
containing the dirty inode was aborted and the log item marked
XFS_LI_ABORTED. The inode was seen as dirty and unpinned, so it
was flushed. IO completion tried to remove the inode from the AIL,
at which point stuff went bad:

XFS (pmem1): Log I/O Error (0x6) detected at xfs_fs_goingdown+0xa3/0xf0 (fs/xfs/xfs_fsops.c:500). Shutting down filesystem.
XFS: Assertion failed: in_ail, file: fs/xfs/xfs_trans_ail.c, line: 67
XFS (pmem1): Please unmount the filesystem and rectify the problem(s)
Workqueue: xfs-buf/pmem1 xfs_buf_ioend_work
RIP: 0010:assfail+0x27/0x2d
Call Trace:
<TASK>
xfs_ail_check+0xa8/0x180
xfs_ail_delete_one+0x3b/0xf0
xfs_buf_inode_iodone+0x329/0x3f0
xfs_buf_ioend+0x1f8/0x530
xfs_buf_ioend_work+0x15/0x20
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>

xfs_trans_commit() needs to check log state for shutdown, not mount
state. It cannot abort dirty log items while the log is still
running as dirty items must remained pinned in memory until they are
either committed to the journal or the log has shut down and they
can be safely tossed away. Hence if the log has not shut down, the
xfs_trans_commit() path must allow completed transactions to commit
to the CIL and pin the dirty items even if a mount shutdown has
started.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_symlink.cdiff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff e6a688c3 Mon Mar 22 10:52:03 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: initialise attr fork on inode create

When we allocate a new inode, we often need to add an attribute to
the inode as part of the create. This can happen as a result of
needing to add default ACLs or security labels before the inode is
made visible to userspace.

This is highly inefficient right now. We do the create transaction
to allocate the inode, then we do an "add attr fork" transaction to
modify the just created empty inode to set the inode fork offset to
allow attributes to be stored, then we go and do the attribute
creation.

This means 3 transactions instead of 1 to allocate an inode, and
this greatly increases the load on the CIL commit code, resulting in
excessive contention on the CIL spin locks and performance
degradation:

18.99% [kernel] [k] __pv_queued_spin_lock_slowpath
3.57% [kernel] [k] do_raw_spin_lock
2.51% [kernel] [k] __raw_callee_save___pv_queued_spin_unlock
2.48% [kernel] [k] memcpy
2.34% [kernel] [k] xfs_log_commit_cil

The typical profile resulting from running fsmark on a selinux enabled
filesytem is adds this overhead to the create path:

- 15.30% xfs_init_security
- 15.23% security_inode_init_security
- 13.05% xfs_initxattrs
- 12.94% xfs_attr_set
- 6.75% xfs_bmap_add_attrfork
- 5.51% xfs_trans_commit
- 5.48% __xfs_trans_commit
- 5.35% xfs_log_commit_cil
- 3.86% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.70% xfs_trans_alloc
0.52% xfs_trans_reserve
- 5.41% xfs_attr_set_args
- 5.39% xfs_attr_set_shortform.constprop.0
- 4.46% xfs_trans_commit
- 4.46% __xfs_trans_commit
- 4.33% xfs_log_commit_cil
- 2.74% _raw_spin_lock
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
0.60% xfs_inode_item_format
0.90% xfs_attr_try_sf_addname
- 1.99% selinux_inode_init_security
- 1.02% security_sid_to_context_force
- 1.00% security_sid_to_context_core
- 0.92% sidtab_entry_to_string
- 0.90% sidtab_sid2str_get
0.59% sidtab_sid2str_put.part.0
- 0.82% selinux_determine_inode_label
- 0.77% security_transition_sid
0.70% security_compute_sid.part.0

And fsmark creation rate performance drops by ~25%. The key point to
note here is that half the additional overhead comes from adding the
attribute fork to the newly created inode. That's crazy, considering
we can do this same thing at inode create time with a couple of
lines of code and no extra overhead.

So, if we know we are going to add an attribute immediately after
creating the inode, let's just initialise the attribute fork inside
the create transaction and chop that whole chunk of code out of
the create fast path. This completely removes the performance
drop caused by enabling SELinux, and the profile looks like:

- 8.99% xfs_init_security
- 9.00% security_inode_init_security
- 6.43% xfs_initxattrs
- 6.37% xfs_attr_set
- 5.45% xfs_attr_set_args
- 5.42% xfs_attr_set_shortform.constprop.0
- 4.51% xfs_trans_commit
- 4.54% __xfs_trans_commit
- 4.59% xfs_log_commit_cil
- 2.67% _raw_spin_lock
- 3.28% do_raw_spin_lock
3.08% __pv_queued_spin_lock_slowpath
0.66% xfs_inode_item_format
- 0.90% xfs_attr_try_sf_addname
- 0.60% xfs_trans_alloc
- 2.35% selinux_inode_init_security
- 1.25% security_sid_to_context_force
- 1.21% security_sid_to_context_core
- 1.19% sidtab_entry_to_string
- 1.20% sidtab_sid2str_get
- 0.86% sidtab_sid2str_put.part.0
- 0.62% _raw_spin_lock_irqsave
- 0.77% do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.84% selinux_determine_inode_label
- 0.83% security_transition_sid
0.86% security_compute_sid.part.0

Which indicates the XFS overhead of creating the selinux xattr has
been halved. This doesn't fix the CIL lock contention problem, just
means it's not a limiting factor for this workload. Lock contention
in the security subsystems is going to be an issue soon, though...

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: fix compilation error when CONFIG_SECURITY=n]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
diff 8aa921a9 Fri Jan 22 17:48:20 MST 2021 Jeffrey Mitchell <jeffrey.mitchell@starlab.io> xfs: set inode size after creating symlink

When XFS creates a new symlink, it writes its size to disk but not to the
VFS inode. This causes i_size_read() to return 0 for that symlink until
it is re-read from disk, for example when the system is rebooted.

I found this inconsistency while protecting directories with eCryptFS.
The command "stat path/to/symlink/in/ecryptfs" will report "Size: 0" if
the symlink was created after the last reboot on an XFS root.

Call i_size_write() in xfs_symlink()

Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 8aa921a9 Fri Jan 22 17:48:20 MST 2021 Jeffrey Mitchell <jeffrey.mitchell@starlab.io> xfs: set inode size after creating symlink

When XFS creates a new symlink, it writes its size to disk but not to the
VFS inode. This causes i_size_read() to return 0 for that symlink until
it is re-read from disk, for example when the system is rebooted.

I found this inconsistency while protecting directories with eCryptFS.
The command "stat path/to/symlink/in/ecryptfs" will report "Size: 0" if
the symlink was created after the last reboot on an XFS root.

Call i_size_write() in xfs_symlink()

Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 0e3eccce Thu Jan 23 18:01:17 MST 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: make xfs_buf_read return an error code

Convert xfs_buf_read() to return numeric error codes like most
everywhere else in xfs.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff a8198666 Wed Aug 01 08:20:32 MDT 2018 Brian Foster <bfoster@redhat.com> xfs: automatic dfops inode relogging

Inodes that are held across deferred operations are explicitly
joined to the dfops structure to ensure appropriate relogging.
While inodes are currently joined explicitly, we can detect the
conditions that require relogging at dfops finish time by inspecting
the transaction item list for inodes with ili_lock_flags == 0.

Replace the xfs_defer_ijoin() infrastructure with such detection and
automatic relogging of held inodes. This eliminates the need for the
per-dfops inode list, replaced by an on-stack variant in
xfs_defer_trans_roll().

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_symlink.hdiff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_sysfs.cdiff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_trace.cdiff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0020a190 Tue Aug 10 19:00:44 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: AIL needs asynchronous CIL forcing

The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.

As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:

....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....

In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.

Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.

The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.

Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.

We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.

One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
H A Dxfs_rtalloc.cdiff ce42b5d3 Sun Dec 17 21:57:22 MST 2023 Christoph Hellwig <hch@lst.de> xfs: return -ENOSPC from xfs_rtallocate_*

Just return -ENOSPC instead of returning 0 and setting the return rt
extent number to NULLRTEXTNO. This is turn removes all users of
NULLRTEXTNO, so remove that as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff a6a38f30 Fri Dec 01 10:17:40 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: make rextslog computation consistent with mkfs

There's a weird discrepancy in xfsprogs dating back to the creation of
the Linux port -- if there are zero rt extents, mkfs will set
sb_rextents and sb_rextslog both to zero:

sbp->sb_rextslog =
(uint8_t)(rtextents ?
libxfs_highbit32((unsigned int)rtextents) : 0);

However, that's not the check that xfs_repair uses for nonzero rtblocks:

if (sb->sb_rextslog !=
libxfs_highbit32((unsigned int)sb->sb_rextents))

The difference here is that xfs_highbit32 returns -1 if its argument is
zero. Unfortunately, this means that in the weird corner case of a
realtime volume shorter than 1 rt extent, xfs_repair will immediately
flag a freshly formatted filesystem as corrupt. Because mkfs has been
writing ondisk artifacts like this for decades, we have to accept that
as "correct". TBH, zero rextslog for zero rtextents makes more sense to
me anyway.

Regrettably, the superblock verifier checks created in commit copied
xfs_repair even though mkfs has been writing out such filesystems for
ages. Fix the superblock verifier to accept what mkfs spits out; the
userspace version of this patch will have to fix xfs_repair as well.

Note that the new helper leaves the zeroday bug where the upper 32 bits
of sb_rextents is ripped off and fed to highbit32. This leads to a
seriously undersized rt summary file, which immediately breaks mkfs:

$ hugedisk.sh foo /dev/sdc $(( 0x100000080 * 4096))B
$ /sbin/mkfs.xfs -f /dev/sda -m rmapbt=0,reflink=0 -r rtdev=/dev/mapper/foo
meta-data=/dev/sda isize=512 agcount=4, agsize=1298176 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=0 bigtime=1 inobtcount=1 nrext64=1
data = bsize=4096 blocks=5192704, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =/dev/mapper/foo extsz=4096 blocks=4294967424, rtextents=4294967424
Discarding blocks...Done.
mkfs.xfs: Error initializing the realtime space [117 - Structure needs cleaning]

The next patch will drop support for rt volumes with fewer than 1 or
more than 2^32-1 rt extents, since they've clearly been broken forever.

Fixes: f8e566c0f5e1f ("xfs: validate the realtime geometry in xfs_validate_sb_common")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
H A Dxfs_stats.hdiff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_stats.cdiff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 18a1e644 Thu Feb 22 01:43:40 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: define an in-memory btree for storing refcount bag info during repairs

Create a new in-memory btree type so that we can store refcount bag info
in a much more memory-efficient and performant format. Recall that the
refcount recordset regenerator computes the new recordset from browsing
the rmap records. Let's say that the rmap records are:

{agbno: 10, length: 40, ...}
{agbno: 11, length: 3, ...}
{agbno: 12, length: 20, ...}
{agbno: 15, length: 1, ...}

It is convenient to have a data structure that could quickly tell us the
refcount for an arbitrary agbno without wasting memory. An array or a
list could do that pretty easily. List suck because of the pointer
overhead. xfarrays are a lot more compact, but we want to minimize
sparse holes in the xfarray to constrain memory usage. Maintaining any
kind of record order isn't needed for correctness, so I created the
"rcbag", which is shorthand for an unordered list of (excerpted) reverse
mappings.

So we add the first rmap to the rcbag, and it looks like:

0: {agbno: 10, length: 40}

The refcount for agbno 10 is 1. Then we move on to block 11, so we add
the second rmap:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}

The refcount for agbno 11 is 2. We move on to block 12, so we add the
third:

0: {agbno: 10, length: 40}
1: {agbno: 11, length: 3}
2: {agbno: 12, length: 20}

The refcount for agbno 12 and 13 is 3. We move on to block 14, and
remove the second rmap:

0: {agbno: 10, length: 40}
1: NULL
2: {agbno: 12, length: 20}

The refcount for agbno 14 is 2. We move on to block 15, and add the
last rmap. But we don't care where it is and we don't want to expand
the array so we put it in slot 1:

0: {agbno: 10, length: 40}
1: {agbno: 15, length: 1}
2: {agbno: 12, length: 20}

The refcount for block 15 is 3. Notice how order doesn't matter in this
list? That's why repair uses an unordered list, or "bag". The data
structure is not a set because it does not guarantee uniqueness.

That said, adding and removing specific items is now an O(n) operation
because we have no idea where that item might be in the list. Overall,
the runtime is O(n^2) which is bad.

I realized that I could easily refactor the btree code and reimplement
the refcount bag with an xfbtree. Adding and removing is now O(log2 n),
so the runtime is at least O(n log2 n), which is much faster. In the
end, the rcbag becomes a sorted list, but that's merely a detail of the
implementation. The repair code doesn't care.

(Note: That horrible xfs_db bmap_inflate command can be used to exercise
this sort of rcbag insanity by cranking up refcounts quickly.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_rmap_item.cdiff 3c919b09 Mon Sep 11 09:39:05 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: reserve less log space when recovering log intent items

Wengang Wang reports that a customer's system was running a number of
truncate operations on a filesystem with a very small log. Contention
on the reserve heads lead to other threads stalling on smaller updates
(e.g. mtime updates) long enough to result in the node being rebooted
on account of the lack of responsivenes. The node failed to recover
because log recovery of an EFI became stuck waiting for a grant of
reserve space. From Wengang's report:

"For the file deletion, log bytes are reserved basing on
xfs_mount->tr_itruncate which is:

tr_logres = 175488,
tr_logcount = 2,
tr_logflags = XFS_TRANS_PERM_LOG_RES,

"You see it's a permanent log reservation with two log operations (two
transactions in rolling mode). After calculation (xlog_calc_unit_res()
adds space for various log headers), the final log space needed per
transaction changes from 175488 to 180208 bytes. So the total log
space needed is 360416 bytes (180208 * 2). [That quantity] of log space
(360416 bytes) needs to be reserved for both run time inode removing
(xfs_inactive_truncate()) and EFI recover (xfs_efi_item_recover())."

In other words, runtime pre-reserves 360K of space in anticipation of
running a chain of two transactions in which each transaction gets a
180K reservation.

Now that we've allocated the transaction, we delete the bmap mapping,
log an EFI to free the space, and roll the transaction as part of
finishing the deferops chain. Rolling creates a new xfs_trans which
shares its ticket with the old transaction. Next, xfs_trans_roll calls
__xfs_trans_commit with regrant == true, which calls xlog_cil_commit
with the same regrant parameter.

xlog_cil_commit calls xfs_log_ticket_regrant, which decrements t_cnt and
subtracts t_curr_res from the reservation and write heads.

If the filesystem is fresh and the first transaction only used (say)
20K, then t_curr_res will be 160K, and we give that much reservation
back to the reservation head. Or if the file is really fragmented and
the first transaction actually uses 170K, then t_curr_res will be 10K,
and that's what we give back to the reservation.

Having done that, we're now headed into the second transaction with an
EFI and 180K of reservation. Other threads apparently consumed all the
reservation for smaller transactions, such as timestamp updates.

Now let's say the first transaction gets written to disk and we crash
without ever completing the second transaction. Now we remount the fs,
log recovery finds the unfinished EFI, and calls xfs_efi_recover to
finish the EFI. However, xfs_efi_recover starts a new tr_itruncate
tranasction, which asks for 360K log reservation. This is a lot more
than the 180K that we had reserved at the time of the crash. If the
first EFI to be recovered is also pinning the tail of the log, we will
be unable to free any space in the log, and recovery livelocks.

Wengang confirmed this:

"Now we have the second transaction which has 180208 log bytes reserved
too. The second transaction is supposed to process intents including
extent freeing. With my hacking patch, I blocked the extent freeing 5
hours. So in that 5 hours, 180208 (NOT 360416) log bytes are reserved.

"With my test case, other transactions (update timestamps) then happen.
As my hacking patch pins the journal tail, those timestamp-updating
transactions finally use up (almost) all the left available log space
(in memory in on disk). And finally the on disk (and in memory)
available log space goes down near to 180208 bytes. Those 180208 bytes
are reserved by [the] second (extent-free) transaction [in the chain]."

Wengang and I noticed that EFI recovery starts a transaction, completes
one step of the chain, and commits the transaction without completing
any other steps of the chain. Those subsequent steps are completed by
xlog_finish_defer_ops, which allocates yet another transaction to
finish the rest of the chain. That transaction gets the same tr_logres
as the head transaction, but with tr_logcount = 1 to force regranting
with every roll to avoid livelocks.

In other words, we already figured this out in commit 929b92f64048d
("xfs: xfs_defer_capture should absorb remaining transaction
reservation"), but should have applied that logic to each intent item's
recovery function. For Wengang's case, the xfs_trans_alloc call in the
EFI recovery function should only be asking for a single transaction's
worth of log reservation -- 180K, not 360K.

Quoting Wengang again:

"With log recovery, during EFI recovery, we use tr_itruncate again to
reserve two transactions that needs 360416 log bytes. Reserving 360416
bytes fails [stalls] because we now only have about 180208 available.

"Actually during the EFI recover, we only need one transaction to free
the extents just like the 2nd transaction at RUNTIME. So it only needs
to reserve 180208 rather than 360416 bytes. We have (a bit) more than
180208 available log bytes on disk, so [if we decrease the reservation
to 180K] the reservation goes and the recovery [finishes]. That is to
say: we can fix the log recover part to fix the issue. We can introduce
a new xfs_trans_res xfs_mount->tr_ext_free

{
tr_logres = 175488,
tr_logcount = 0,
tr_logflags = 0,
}

"and use tr_ext_free instead of tr_itruncate in EFI recover."

However, I don't think it quite makes sense to create an entirely new
transaction reservation type to handle single-stepping during log
recovery. Instead, we should copy the transaction reservation
information in the xfs_mount, change tr_logcount to 1, and pass that
into xfs_trans_alloc. We know this won't risk changing the min log size
computation since we always ask for a fraction of the reservation for
all known transaction types.

This looks like it's been lurking in the codebase since commit
3d3c8b5222b92, which changed the xfs_trans_reserve call in
xlog_recover_process_efi to use the tr_logcount in tr_itruncate.
That changed the EFI recovery transaction from making a
non-XFS_TRANS_PERM_LOG_RES request for one transaction's worth of log
space to a XFS_TRANS_PERM_LOG_RES request for two transactions worth.

Fixes: 3d3c8b5222b92 ("xfs: refactor xfs_trans_reserve() interface")
Complements: 929b92f64048d ("xfs: xfs_defer_capture should absorb remaining transaction reservation")
Suggested-by: Wengang Wang <wen.gang.wang@oracle.com>
Cc: Srikanth C S <srikanth.c.s@oracle.com>
[djwong: apply the same transformation to all log intent recovery]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 3c919b09 Mon Sep 11 09:39:05 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: reserve less log space when recovering log intent items

Wengang Wang reports that a customer's system was running a number of
truncate operations on a filesystem with a very small log. Contention
on the reserve heads lead to other threads stalling on smaller updates
(e.g. mtime updates) long enough to result in the node being rebooted
on account of the lack of responsivenes. The node failed to recover
because log recovery of an EFI became stuck waiting for a grant of
reserve space. From Wengang's report:

"For the file deletion, log bytes are reserved basing on
xfs_mount->tr_itruncate which is:

tr_logres = 175488,
tr_logcount = 2,
tr_logflags = XFS_TRANS_PERM_LOG_RES,

"You see it's a permanent log reservation with two log operations (two
transactions in rolling mode). After calculation (xlog_calc_unit_res()
adds space for various log headers), the final log space needed per
transaction changes from 175488 to 180208 bytes. So the total log
space needed is 360416 bytes (180208 * 2). [That quantity] of log space
(360416 bytes) needs to be reserved for both run time inode removing
(xfs_inactive_truncate()) and EFI recover (xfs_efi_item_recover())."

In other words, runtime pre-reserves 360K of space in anticipation of
running a chain of two transactions in which each transaction gets a
180K reservation.

Now that we've allocated the transaction, we delete the bmap mapping,
log an EFI to free the space, and roll the transaction as part of
finishing the deferops chain. Rolling creates a new xfs_trans which
shares its ticket with the old transaction. Next, xfs_trans_roll calls
__xfs_trans_commit with regrant == true, which calls xlog_cil_commit
with the same regrant parameter.

xlog_cil_commit calls xfs_log_ticket_regrant, which decrements t_cnt and
subtracts t_curr_res from the reservation and write heads.

If the filesystem is fresh and the first transaction only used (say)
20K, then t_curr_res will be 160K, and we give that much reservation
back to the reservation head. Or if the file is really fragmented and
the first transaction actually uses 170K, then t_curr_res will be 10K,
and that's what we give back to the reservation.

Having done that, we're now headed into the second transaction with an
EFI and 180K of reservation. Other threads apparently consumed all the
reservation for smaller transactions, such as timestamp updates.

Now let's say the first transaction gets written to disk and we crash
without ever completing the second transaction. Now we remount the fs,
log recovery finds the unfinished EFI, and calls xfs_efi_recover to
finish the EFI. However, xfs_efi_recover starts a new tr_itruncate
tranasction, which asks for 360K log reservation. This is a lot more
than the 180K that we had reserved at the time of the crash. If the
first EFI to be recovered is also pinning the tail of the log, we will
be unable to free any space in the log, and recovery livelocks.

Wengang confirmed this:

"Now we have the second transaction which has 180208 log bytes reserved
too. The second transaction is supposed to process intents including
extent freeing. With my hacking patch, I blocked the extent freeing 5
hours. So in that 5 hours, 180208 (NOT 360416) log bytes are reserved.

"With my test case, other transactions (update timestamps) then happen.
As my hacking patch pins the journal tail, those timestamp-updating
transactions finally use up (almost) all the left available log space
(in memory in on disk). And finally the on disk (and in memory)
available log space goes down near to 180208 bytes. Those 180208 bytes
are reserved by [the] second (extent-free) transaction [in the chain]."

Wengang and I noticed that EFI recovery starts a transaction, completes
one step of the chain, and commits the transaction without completing
any other steps of the chain. Those subsequent steps are completed by
xlog_finish_defer_ops, which allocates yet another transaction to
finish the rest of the chain. That transaction gets the same tr_logres
as the head transaction, but with tr_logcount = 1 to force regranting
with every roll to avoid livelocks.

In other words, we already figured this out in commit 929b92f64048d
("xfs: xfs_defer_capture should absorb remaining transaction
reservation"), but should have applied that logic to each intent item's
recovery function. For Wengang's case, the xfs_trans_alloc call in the
EFI recovery function should only be asking for a single transaction's
worth of log reservation -- 180K, not 360K.

Quoting Wengang again:

"With log recovery, during EFI recovery, we use tr_itruncate again to
reserve two transactions that needs 360416 log bytes. Reserving 360416
bytes fails [stalls] because we now only have about 180208 available.

"Actually during the EFI recover, we only need one transaction to free
the extents just like the 2nd transaction at RUNTIME. So it only needs
to reserve 180208 rather than 360416 bytes. We have (a bit) more than
180208 available log bytes on disk, so [if we decrease the reservation
to 180K] the reservation goes and the recovery [finishes]. That is to
say: we can fix the log recover part to fix the issue. We can introduce
a new xfs_trans_res xfs_mount->tr_ext_free

{
tr_logres = 175488,
tr_logcount = 0,
tr_logflags = 0,
}

"and use tr_ext_free instead of tr_itruncate in EFI recover."

However, I don't think it quite makes sense to create an entirely new
transaction reservation type to handle single-stepping during log
recovery. Instead, we should copy the transaction reservation
information in the xfs_mount, change tr_logcount to 1, and pass that
into xfs_trans_alloc. We know this won't risk changing the min log size
computation since we always ask for a fraction of the reservation for
all known transaction types.

This looks like it's been lurking in the codebase since commit
3d3c8b5222b92, which changed the xfs_trans_reserve call in
xlog_recover_process_efi to use the tr_logcount in tr_itruncate.
That changed the EFI recovery transaction from making a
non-XFS_TRANS_PERM_LOG_RES request for one transaction's worth of log
space to a XFS_TRANS_PERM_LOG_RES request for two transactions worth.

Fixes: 3d3c8b5222b92 ("xfs: refactor xfs_trans_reserve() interface")
Complements: 929b92f64048d ("xfs: xfs_defer_capture should absorb remaining transaction reservation")
Suggested-by: Wengang Wang <wen.gang.wang@oracle.com>
Cc: Srikanth C S <srikanth.c.s@oracle.com>
[djwong: apply the same transformation to all log intent recovery]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 707e0dda Mon Aug 26 01:06:22 MDT 2019 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> fs: xfs: Remove KM_NOSLEEP and KM_SLEEP.

Since no caller is using KM_NOSLEEP and no callee branches on KM_SLEEP,
we can remove KM_NOSLEEP and replace KM_SLEEP with 0.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
H A Dxfs_reflink.cdiff d6211330 Thu Aug 04 09:59:27 MDT 2022 Chandan Babu R <chandan.babu@oracle.com> xfs: Fix false ENOSPC when performing direct write on a delalloc extent in cow fork

On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.

This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.

In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.

The following script reliably recreates the bug described above.

#!/usr/bin/bash

device=/dev/loop0
shortdev=$(basename $device)

mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating

errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent

umount $device > /dev/null 2>&1

echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi

echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi

echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1

sync

echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null

echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1

echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile

echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag

echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1

sync

echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1

This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.

Fixes: 3c68d44a2b49 ("xfs: allocate direct I/O COW blocks in iomap_begin")
Reported-and-Root-caused-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: slight editing to make the locking less grody, and fix some style things]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff d6211330 Thu Aug 04 09:59:27 MDT 2022 Chandan Babu R <chandan.babu@oracle.com> xfs: Fix false ENOSPC when performing direct write on a delalloc extent in cow fork

On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.

This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.

In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.

The following script reliably recreates the bug described above.

#!/usr/bin/bash

device=/dev/loop0
shortdev=$(basename $device)

mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating

errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent

umount $device > /dev/null 2>&1

echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi

echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi

echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1

sync

echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null

echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1

echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile

echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag

echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1

sync

echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1

This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.

Fixes: 3c68d44a2b49 ("xfs: allocate direct I/O COW blocks in iomap_begin")
Reported-and-Root-caused-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: slight editing to make the locking less grody, and fix some style things]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff d6211330 Thu Aug 04 09:59:27 MDT 2022 Chandan Babu R <chandan.babu@oracle.com> xfs: Fix false ENOSPC when performing direct write on a delalloc extent in cow fork

On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.

This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.

In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.

The following script reliably recreates the bug described above.

#!/usr/bin/bash

device=/dev/loop0
shortdev=$(basename $device)

mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating

errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent

umount $device > /dev/null 2>&1

echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi

echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi

echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1

sync

echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null

echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1

echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile

echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag

echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1

sync

echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1

This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.

Fixes: 3c68d44a2b49 ("xfs: allocate direct I/O COW blocks in iomap_begin")
Reported-and-Root-caused-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: slight editing to make the locking less grody, and fix some style things]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff d6211330 Thu Aug 04 09:59:27 MDT 2022 Chandan Babu R <chandan.babu@oracle.com> xfs: Fix false ENOSPC when performing direct write on a delalloc extent in cow fork

On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.

This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.

In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.

The following script reliably recreates the bug described above.

#!/usr/bin/bash

device=/dev/loop0
shortdev=$(basename $device)

mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating

errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent

umount $device > /dev/null 2>&1

echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi

echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi

echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1

sync

echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null

echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1

echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile

echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag

echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1

sync

echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1

This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.

Fixes: 3c68d44a2b49 ("xfs: allocate direct I/O COW blocks in iomap_begin")
Reported-and-Root-caused-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: slight editing to make the locking less grody, and fix some style things]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff d6211330 Thu Aug 04 09:59:27 MDT 2022 Chandan Babu R <chandan.babu@oracle.com> xfs: Fix false ENOSPC when performing direct write on a delalloc extent in cow fork

On a higly fragmented filesystem a Direct IO write can fail with -ENOSPC error
even though the filesystem has sufficient number of free blocks.

This occurs if the file offset range on which the write operation is being
performed has a delalloc extent in the cow fork and this delalloc extent
begins much before the Direct IO range.

In such a scenario, xfs_reflink_allocate_cow() invokes xfs_bmapi_write() to
allocate the blocks mapped by the delalloc extent. The extent thus allocated
may not cover the beginning of file offset range on which the Direct IO write
was issued. Hence xfs_reflink_allocate_cow() ends up returning -ENOSPC.

The following script reliably recreates the bug described above.

#!/usr/bin/bash

device=/dev/loop0
shortdev=$(basename $device)

mntpnt=/mnt/
file1=${mntpnt}/file1
file2=${mntpnt}/file2
fragmentedfile=${mntpnt}/fragmentedfile
punchprog=/root/repos/xfstests-dev/src/punch-alternating

errortag=/sys/fs/xfs/${shortdev}/errortag/bmap_alloc_minlen_extent

umount $device > /dev/null 2>&1

echo "Create FS"
mkfs.xfs -f -m reflink=1 $device > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mkfs failed."
exit 1
fi

echo "Mount FS"
mount $device $mntpnt > /dev/null 2>&1
if [[ $? != 0 ]]; then
echo "mount failed."
exit 1
fi

echo "Create source file"
xfs_io -f -c "pwrite 0 32M" $file1 > /dev/null 2>&1

sync

echo "Create Reflinked file"
xfs_io -f -c "reflink $file1" $file2 &>/dev/null

echo "Set cowextsize"
xfs_io -c "cowextsize 16M" $file1 > /dev/null 2>&1

echo "Fragment FS"
xfs_io -f -c "pwrite 0 64M" $fragmentedfile > /dev/null 2>&1
sync
$punchprog $fragmentedfile

echo "Allocate block sized extent from now onwards"
echo -n 1 > $errortag

echo "Create 16MiB delalloc extent in CoW fork"
xfs_io -c "pwrite 0 4k" $file1 > /dev/null 2>&1

sync

echo "Direct I/O write at offset 12k"
xfs_io -d -c "pwrite 12k 8k" $file1

This commit fixes the bug by invoking xfs_bmapi_write() in a loop until disk
blocks are allocated for atleast the starting file offset of the Direct IO
write range.

Fixes: 3c68d44a2b49 ("xfs: allocate direct I/O COW blocks in iomap_begin")
Reported-and-Root-caused-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: slight editing to make the locking less grody, and fix some style things]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 7993f1a4 Wed Dec 15 12:52:23 MST 2021 Darrick J. Wong <djwong@kernel.org> xfs: only run COW extent recovery when there are no live extents

As part of multiple customer escalations due to file data corruption
after copy on write operations, I wrote some fstests that use fsstress
to hammer on COW to shake things loose. Regrettably, I caught some
filesystem shutdowns due to incorrect rmap operations with the following
loop:

mount <filesystem> # (0)
fsstress <run only readonly ops> & # (1)
while true; do
fsstress <run all ops>
mount -o remount,ro # (2)
fsstress <run only readonly ops>
mount -o remount,rw # (3)
done

When (2) happens, notice that (1) is still running. xfs_remount_ro will
call xfs_blockgc_stop to walk the inode cache to free all the COW
extents, but the blockgc mechanism races with (1)'s reader threads to
take IOLOCKs and loses, which means that it doesn't clean them all out.
Call such a file (A).

When (3) happens, xfs_remount_rw calls xfs_reflink_recover_cow, which
walks the ondisk refcount btree and frees any COW extent that it finds.
This function does not check the inode cache, which means that incore
COW forks of inode (A) is now inconsistent with the ondisk metadata. If
one of those former COW extents are allocated and mapped into another
file (B) and someone triggers a COW to the stale reservation in (A), A's
dirty data will be written into (B) and once that's done, those blocks
will be transferred to (A)'s data fork without bumping the refcount.

The results are catastrophic -- file (B) and the refcount btree are now
corrupt. In the first patch, we fixed the race condition in (2) so that
(A) will always flush the COW fork. In this second patch, we move the
_recover_cow call to the initial mount call in (0) for safety.

As mentioned previously, xfs_reflink_recover_cow walks the refcount
btree looking for COW staging extents, and frees them. This was
intended to be run at mount time (when we know there are no live inodes)
to clean up any leftover staging events that may have been left behind
during an unclean shutdown. As a time "optimization" for readonly
mounts, we deferred this to the ro->rw transition, not realizing that
any failure to clean all COW forks during a rw->ro transition would
result in catastrophic corruption.

Therefore, remove this optimization and only run the recovery routine
when we're guaranteed not to have any COW staging extents anywhere,
which means we always run this at mount time. While we're at it, move
the callsite to xfs_log_mount_finish because any refcount btree
expansion (however unlikely given that we're removing records from the
right side of the index) must be fed by a per-AG reservation, which
doesn't exist in its current location.

Fixes: 174edb0e46e5 ("xfs: store in-progress CoW allocations in the refcount btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 7993f1a4 Wed Dec 15 12:52:23 MST 2021 Darrick J. Wong <djwong@kernel.org> xfs: only run COW extent recovery when there are no live extents

As part of multiple customer escalations due to file data corruption
after copy on write operations, I wrote some fstests that use fsstress
to hammer on COW to shake things loose. Regrettably, I caught some
filesystem shutdowns due to incorrect rmap operations with the following
loop:

mount <filesystem> # (0)
fsstress <run only readonly ops> & # (1)
while true; do
fsstress <run all ops>
mount -o remount,ro # (2)
fsstress <run only readonly ops>
mount -o remount,rw # (3)
done

When (2) happens, notice that (1) is still running. xfs_remount_ro will
call xfs_blockgc_stop to walk the inode cache to free all the COW
extents, but the blockgc mechanism races with (1)'s reader threads to
take IOLOCKs and loses, which means that it doesn't clean them all out.
Call such a file (A).

When (3) happens, xfs_remount_rw calls xfs_reflink_recover_cow, which
walks the ondisk refcount btree and frees any COW extent that it finds.
This function does not check the inode cache, which means that incore
COW forks of inode (A) is now inconsistent with the ondisk metadata. If
one of those former COW extents are allocated and mapped into another
file (B) and someone triggers a COW to the stale reservation in (A), A's
dirty data will be written into (B) and once that's done, those blocks
will be transferred to (A)'s data fork without bumping the refcount.

The results are catastrophic -- file (B) and the refcount btree are now
corrupt. In the first patch, we fixed the race condition in (2) so that
(A) will always flush the COW fork. In this second patch, we move the
_recover_cow call to the initial mount call in (0) for safety.

As mentioned previously, xfs_reflink_recover_cow walks the refcount
btree looking for COW staging extents, and frees them. This was
intended to be run at mount time (when we know there are no live inodes)
to clean up any leftover staging events that may have been left behind
during an unclean shutdown. As a time "optimization" for readonly
mounts, we deferred this to the ro->rw transition, not realizing that
any failure to clean all COW forks during a rw->ro transition would
result in catastrophic corruption.

Therefore, remove this optimization and only run the recovery routine
when we're guaranteed not to have any COW staging extents anywhere,
which means we always run this at mount time. While we're at it, move
the callsite to xfs_log_mount_finish because any refcount btree
expansion (however unlikely given that we're removing records from the
right side of the index) must be fed by a per-AG reservation, which
doesn't exist in its current location.

Fixes: 174edb0e46e5 ("xfs: store in-progress CoW allocations in the refcount btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff aa124436 Mon Jan 20 15:34:47 MST 2020 zhengbin <zhengbin13@huawei.com> xfs: change return value of xfs_inode_need_cow to int

Fixes coccicheck warning:

fs/xfs/xfs_reflink.c:236:9-10: WARNING: return of 0/1 in function 'xfs_inode_need_cow' with return type bool

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
[darrick: rename the function so it doesn't sound like a predicate]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 66ae56a5 Mon Feb 18 10:38:49 MST 2019 Christoph Hellwig <hch@lst.de> xfs: introduce an always_cow mode

Add a mode where XFS never overwrites existing blocks in place. This
is to aid debugging our COW code, and also put infatructure in place
for things like possible future support for zoned block devices, which
can't support overwrites.

This mode is enabled globally by doing a:

echo 1 > /sys/fs/xfs/debug/always_cow

Note that the parameter is global to allow running all tests in xfstests
easily in this mode, which would not easily be possible with a per-fs
sysfs file.

In always_cow mode persistent preallocations are disabled, and fallocate
will fail when called with a 0 mode (with our without
FALLOC_FL_KEEP_SIZE), and not create unwritten extent for zeroed space
when called with FALLOC_FL_ZERO_RANGE or FALLOC_FL_UNSHARE_RANGE.

There are a few interesting xfstests failures when run in always_cow
mode:

- generic/392 fails because the bytes used in the file used to test
hole punch recovery are less after the log replay. This is
because the blocks written and then punched out are only freed
with a delay due to the logging mechanism.
- xfs/170 will fail as the already fragile file streams mechanism
doesn't seem to interact well with the COW allocator
- xfs/180 xfs/182 xfs/192 xfs/198 xfs/204 and xfs/208 will claim
the file system is badly fragmented, but there is not much we
can do to avoid that when always writing out of place
- xfs/205 fails because overwriting a file in always_cow mode
will require new space allocation and the assumption in the
test thus don't work anymore.
- xfs/326 fails to modify the file at all in always_cow mode after
injecting the refcount error, leading to an unexpected md5sum
after the remount, but that again is expected

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff d6f215f3 Wed Dec 12 09:46:19 MST 2018 Darrick J. Wong <darrick.wong@oracle.com> xfs: split up the xfs_reflink_end_cow work into smaller transactions

In xfs_reflink_end_cow, we allocate a single transaction for the entire
end_cow operation and then loop the CoW fork mappings to move them to
the data fork. This design fails on a heavily fragmented filesystem
where an inode's data fork has exactly one more extent than would fit in
an extents-format fork, because the unmap can collapse the data fork
into extents format (freeing the bmbt block) but the remap can expand
the data fork back into a (newly allocated) bmbt block. If the number
of extents we end up remapping is large, we can overflow the block
reservation because we reserved blocks assuming that we were adding
mappings into an already-cleared area of the data fork.

Let's say we have 8 extents in the data fork, 8 extents in the CoW fork,
and the data fork can hold at most 7 extents before needing to convert
to btree format; and that blocks A-P are discontiguous single-block
extents:

0......7
D: ABCDEFGH
C: IJKLMNOP

When a write to file blocks 0-7 completes, we must remap I-P into the
data fork. We start by removing H from the btree-format data fork. Now
we have 7 extents, so we convert the fork to extents format, freeing the
bmbt block. We then move P into the data fork and it now has 8 extents
again. We must convert the data fork back to btree format, requiring a
block allocation. If we repeat this sequence for blocks 6-5-4-3-2-1-0,
we'll need a total of 8 block allocations to remap all 8 blocks. We
reserved only enough blocks to handle one btree split (5 blocks on a 4k
block filesystem), which means we overflow the block reservation.

To fix this issue, create a separate helper function to remap a single
extent, and change _reflink_end_cow to call it in a tight loop over the
entire range we're completing. As a side effect this also removes the
size restrictions on how many extents we can end_cow at a time, though
nobody ever hit that. It is not reasonable to reserve N blocks to remap
N blocks.

Note that this can be reproduced after ~320 million fsx ops while
running generic/938 (long soak directio fsx exerciser):

XFS: Assertion failed: tp->t_blk_res >= tp->t_blk_res_used, file: fs/xfs/xfs_trans.c, line: 116
<machine registers snipped>
Call Trace:
xfs_trans_dup+0x211/0x250 [xfs]
xfs_trans_roll+0x6d/0x180 [xfs]
xfs_defer_trans_roll+0x10c/0x3b0 [xfs]
xfs_defer_finish_noroll+0xdf/0x740 [xfs]
xfs_defer_finish+0x13/0x70 [xfs]
xfs_reflink_end_cow+0x2c6/0x680 [xfs]
xfs_dio_write_end_io+0x115/0x220 [xfs]
iomap_dio_complete+0x3f/0x130
iomap_dio_rw+0x3c3/0x420
xfs_file_dio_aio_write+0x132/0x3c0 [xfs]
xfs_file_write_iter+0x8b/0xc0 [xfs]
__vfs_write+0x193/0x1f0
vfs_write+0xba/0x1c0
ksys_write+0x52/0xc0
do_syscall_64+0x50/0x160
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
H A Dxfs_refcount_item.cdiff 3c919b09 Mon Sep 11 09:39:05 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: reserve less log space when recovering log intent items

Wengang Wang reports that a customer's system was running a number of
truncate operations on a filesystem with a very small log. Contention
on the reserve heads lead to other threads stalling on smaller updates
(e.g. mtime updates) long enough to result in the node being rebooted
on account of the lack of responsivenes. The node failed to recover
because log recovery of an EFI became stuck waiting for a grant of
reserve space. From Wengang's report:

"For the file deletion, log bytes are reserved basing on
xfs_mount->tr_itruncate which is:

tr_logres = 175488,
tr_logcount = 2,
tr_logflags = XFS_TRANS_PERM_LOG_RES,

"You see it's a permanent log reservation with two log operations (two
transactions in rolling mode). After calculation (xlog_calc_unit_res()
adds space for various log headers), the final log space needed per
transaction changes from 175488 to 180208 bytes. So the total log
space needed is 360416 bytes (180208 * 2). [That quantity] of log space
(360416 bytes) needs to be reserved for both run time inode removing
(xfs_inactive_truncate()) and EFI recover (xfs_efi_item_recover())."

In other words, runtime pre-reserves 360K of space in anticipation of
running a chain of two transactions in which each transaction gets a
180K reservation.

Now that we've allocated the transaction, we delete the bmap mapping,
log an EFI to free the space, and roll the transaction as part of
finishing the deferops chain. Rolling creates a new xfs_trans which
shares its ticket with the old transaction. Next, xfs_trans_roll calls
__xfs_trans_commit with regrant == true, which calls xlog_cil_commit
with the same regrant parameter.

xlog_cil_commit calls xfs_log_ticket_regrant, which decrements t_cnt and
subtracts t_curr_res from the reservation and write heads.

If the filesystem is fresh and the first transaction only used (say)
20K, then t_curr_res will be 160K, and we give that much reservation
back to the reservation head. Or if the file is really fragmented and
the first transaction actually uses 170K, then t_curr_res will be 10K,
and that's what we give back to the reservation.

Having done that, we're now headed into the second transaction with an
EFI and 180K of reservation. Other threads apparently consumed all the
reservation for smaller transactions, such as timestamp updates.

Now let's say the first transaction gets written to disk and we crash
without ever completing the second transaction. Now we remount the fs,
log recovery finds the unfinished EFI, and calls xfs_efi_recover to
finish the EFI. However, xfs_efi_recover starts a new tr_itruncate
tranasction, which asks for 360K log reservation. This is a lot more
than the 180K that we had reserved at the time of the crash. If the
first EFI to be recovered is also pinning the tail of the log, we will
be unable to free any space in the log, and recovery livelocks.

Wengang confirmed this:

"Now we have the second transaction which has 180208 log bytes reserved
too. The second transaction is supposed to process intents including
extent freeing. With my hacking patch, I blocked the extent freeing 5
hours. So in that 5 hours, 180208 (NOT 360416) log bytes are reserved.

"With my test case, other transactions (update timestamps) then happen.
As my hacking patch pins the journal tail, those timestamp-updating
transactions finally use up (almost) all the left available log space
(in memory in on disk). And finally the on disk (and in memory)
available log space goes down near to 180208 bytes. Those 180208 bytes
are reserved by [the] second (extent-free) transaction [in the chain]."

Wengang and I noticed that EFI recovery starts a transaction, completes
one step of the chain, and commits the transaction without completing
any other steps of the chain. Those subsequent steps are completed by
xlog_finish_defer_ops, which allocates yet another transaction to
finish the rest of the chain. That transaction gets the same tr_logres
as the head transaction, but with tr_logcount = 1 to force regranting
with every roll to avoid livelocks.

In other words, we already figured this out in commit 929b92f64048d
("xfs: xfs_defer_capture should absorb remaining transaction
reservation"), but should have applied that logic to each intent item's
recovery function. For Wengang's case, the xfs_trans_alloc call in the
EFI recovery function should only be asking for a single transaction's
worth of log reservation -- 180K, not 360K.

Quoting Wengang again:

"With log recovery, during EFI recovery, we use tr_itruncate again to
reserve two transactions that needs 360416 log bytes. Reserving 360416
bytes fails [stalls] because we now only have about 180208 available.

"Actually during the EFI recover, we only need one transaction to free
the extents just like the 2nd transaction at RUNTIME. So it only needs
to reserve 180208 rather than 360416 bytes. We have (a bit) more than
180208 available log bytes on disk, so [if we decrease the reservation
to 180K] the reservation goes and the recovery [finishes]. That is to
say: we can fix the log recover part to fix the issue. We can introduce
a new xfs_trans_res xfs_mount->tr_ext_free

{
tr_logres = 175488,
tr_logcount = 0,
tr_logflags = 0,
}

"and use tr_ext_free instead of tr_itruncate in EFI recover."

However, I don't think it quite makes sense to create an entirely new
transaction reservation type to handle single-stepping during log
recovery. Instead, we should copy the transaction reservation
information in the xfs_mount, change tr_logcount to 1, and pass that
into xfs_trans_alloc. We know this won't risk changing the min log size
computation since we always ask for a fraction of the reservation for
all known transaction types.

This looks like it's been lurking in the codebase since commit
3d3c8b5222b92, which changed the xfs_trans_reserve call in
xlog_recover_process_efi to use the tr_logcount in tr_itruncate.
That changed the EFI recovery transaction from making a
non-XFS_TRANS_PERM_LOG_RES request for one transaction's worth of log
space to a XFS_TRANS_PERM_LOG_RES request for two transactions worth.

Fixes: 3d3c8b5222b92 ("xfs: refactor xfs_trans_reserve() interface")
Complements: 929b92f64048d ("xfs: xfs_defer_capture should absorb remaining transaction reservation")
Suggested-by: Wengang Wang <wen.gang.wang@oracle.com>
Cc: Srikanth C S <srikanth.c.s@oracle.com>
[djwong: apply the same transformation to all log intent recovery]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 3c919b09 Mon Sep 11 09:39:05 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: reserve less log space when recovering log intent items

Wengang Wang reports that a customer's system was running a number of
truncate operations on a filesystem with a very small log. Contention
on the reserve heads lead to other threads stalling on smaller updates
(e.g. mtime updates) long enough to result in the node being rebooted
on account of the lack of responsivenes. The node failed to recover
because log recovery of an EFI became stuck waiting for a grant of
reserve space. From Wengang's report:

"For the file deletion, log bytes are reserved basing on
xfs_mount->tr_itruncate which is:

tr_logres = 175488,
tr_logcount = 2,
tr_logflags = XFS_TRANS_PERM_LOG_RES,

"You see it's a permanent log reservation with two log operations (two
transactions in rolling mode). After calculation (xlog_calc_unit_res()
adds space for various log headers), the final log space needed per
transaction changes from 175488 to 180208 bytes. So the total log
space needed is 360416 bytes (180208 * 2). [That quantity] of log space
(360416 bytes) needs to be reserved for both run time inode removing
(xfs_inactive_truncate()) and EFI recover (xfs_efi_item_recover())."

In other words, runtime pre-reserves 360K of space in anticipation of
running a chain of two transactions in which each transaction gets a
180K reservation.

Now that we've allocated the transaction, we delete the bmap mapping,
log an EFI to free the space, and roll the transaction as part of
finishing the deferops chain. Rolling creates a new xfs_trans which
shares its ticket with the old transaction. Next, xfs_trans_roll calls
__xfs_trans_commit with regrant == true, which calls xlog_cil_commit
with the same regrant parameter.

xlog_cil_commit calls xfs_log_ticket_regrant, which decrements t_cnt and
subtracts t_curr_res from the reservation and write heads.

If the filesystem is fresh and the first transaction only used (say)
20K, then t_curr_res will be 160K, and we give that much reservation
back to the reservation head. Or if the file is really fragmented and
the first transaction actually uses 170K, then t_curr_res will be 10K,
and that's what we give back to the reservation.

Having done that, we're now headed into the second transaction with an
EFI and 180K of reservation. Other threads apparently consumed all the
reservation for smaller transactions, such as timestamp updates.

Now let's say the first transaction gets written to disk and we crash
without ever completing the second transaction. Now we remount the fs,
log recovery finds the unfinished EFI, and calls xfs_efi_recover to
finish the EFI. However, xfs_efi_recover starts a new tr_itruncate
tranasction, which asks for 360K log reservation. This is a lot more
than the 180K that we had reserved at the time of the crash. If the
first EFI to be recovered is also pinning the tail of the log, we will
be unable to free any space in the log, and recovery livelocks.

Wengang confirmed this:

"Now we have the second transaction which has 180208 log bytes reserved
too. The second transaction is supposed to process intents including
extent freeing. With my hacking patch, I blocked the extent freeing 5
hours. So in that 5 hours, 180208 (NOT 360416) log bytes are reserved.

"With my test case, other transactions (update timestamps) then happen.
As my hacking patch pins the journal tail, those timestamp-updating
transactions finally use up (almost) all the left available log space
(in memory in on disk). And finally the on disk (and in memory)
available log space goes down near to 180208 bytes. Those 180208 bytes
are reserved by [the] second (extent-free) transaction [in the chain]."

Wengang and I noticed that EFI recovery starts a transaction, completes
one step of the chain, and commits the transaction without completing
any other steps of the chain. Those subsequent steps are completed by
xlog_finish_defer_ops, which allocates yet another transaction to
finish the rest of the chain. That transaction gets the same tr_logres
as the head transaction, but with tr_logcount = 1 to force regranting
with every roll to avoid livelocks.

In other words, we already figured this out in commit 929b92f64048d
("xfs: xfs_defer_capture should absorb remaining transaction
reservation"), but should have applied that logic to each intent item's
recovery function. For Wengang's case, the xfs_trans_alloc call in the
EFI recovery function should only be asking for a single transaction's
worth of log reservation -- 180K, not 360K.

Quoting Wengang again:

"With log recovery, during EFI recovery, we use tr_itruncate again to
reserve two transactions that needs 360416 log bytes. Reserving 360416
bytes fails [stalls] because we now only have about 180208 available.

"Actually during the EFI recover, we only need one transaction to free
the extents just like the 2nd transaction at RUNTIME. So it only needs
to reserve 180208 rather than 360416 bytes. We have (a bit) more than
180208 available log bytes on disk, so [if we decrease the reservation
to 180K] the reservation goes and the recovery [finishes]. That is to
say: we can fix the log recover part to fix the issue. We can introduce
a new xfs_trans_res xfs_mount->tr_ext_free

{
tr_logres = 175488,
tr_logcount = 0,
tr_logflags = 0,
}

"and use tr_ext_free instead of tr_itruncate in EFI recover."

However, I don't think it quite makes sense to create an entirely new
transaction reservation type to handle single-stepping during log
recovery. Instead, we should copy the transaction reservation
information in the xfs_mount, change tr_logcount to 1, and pass that
into xfs_trans_alloc. We know this won't risk changing the min log size
computation since we always ask for a fraction of the reservation for
all known transaction types.

This looks like it's been lurking in the codebase since commit
3d3c8b5222b92, which changed the xfs_trans_reserve call in
xlog_recover_process_efi to use the tr_logcount in tr_itruncate.
That changed the EFI recovery transaction from making a
non-XFS_TRANS_PERM_LOG_RES request for one transaction's worth of log
space to a XFS_TRANS_PERM_LOG_RES request for two transactions worth.

Fixes: 3d3c8b5222b92 ("xfs: refactor xfs_trans_reserve() interface")
Complements: 929b92f64048d ("xfs: xfs_defer_capture should absorb remaining transaction reservation")
Suggested-by: Wengang Wang <wen.gang.wang@oracle.com>
Cc: Srikanth C S <srikanth.c.s@oracle.com>
[djwong: apply the same transformation to all log intent recovery]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 0b11553e Wed Feb 01 11:16:04 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: pass refcount intent directly through the log intent code

Pass the incore refcount intent through the CUI logging code instead of
repeatedly boxing and unboxing parameters.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0d79781a Sun Nov 29 17:33:37 MST 2020 Darrick J. Wong <darrick.wong@oracle.com> xfs: improve the code that checks recovered refcount intent items

The code that validates recovered refcount intent items is kind of a
mess -- it doesn't use the standard xfs type validators, and it doesn't
check for things that it should. Fix the validator function to use the
standard validation helpers and look for more types of obvious errors.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
diff 707e0dda Mon Aug 26 01:06:22 MDT 2019 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> fs: xfs: Remove KM_NOSLEEP and KM_SLEEP.

Since no caller is using KM_NOSLEEP and no callee branches on KM_SLEEP,
we can remove KM_NOSLEEP and replace KM_SLEEP with 0.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0f37d178 Wed Aug 01 08:20:34 MDT 2018 Brian Foster <bfoster@redhat.com> xfs: pass transaction to xfs_defer_add()

The majority of remaining references to struct xfs_defer_ops in XFS
are associated with xfs_defer_add(). At this point, there are no
more external xfs_defer_ops users left. All instances of
xfs_defer_ops are embedded in the transaction, which means we can
safely pass the transaction down to the dfops add interface.

Update xfs_defer_add() to receive the transaction as a parameter.
Various subsystems implement wrappers to allocate and construct the
context specific data structures for the associated deferred
operation type. Update these to also carry the transaction down as
needed and clean up unused dfops parameters along the way.

This removes most of the remaining references to struct
xfs_defer_ops throughout the code and facilitates removal of the
structure.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[darrick: fix unused variable warnings with ftrace disabled]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
/linux-master/fs/xfs/scrub/
H A Dcommon.cdiff 6c728952 Fri Dec 15 11:03:37 MST 2023 Darrick J. Wong <djwong@kernel.org> xfs: abort directory parent scrub scans if we encounter a zapped directory

In a previous patch, we added some code to perform sufficient repairs
to an ondisk inode record such that the inode cache would be willing to
load the inode. If the broken inode was a shortform directory, it will
reset the directory to something plausible, which is to say an empty
subdirectory of the root. The telltale signs that something is
seriously wrong is the broken link count.

Such directories look clean, but they shouldn't participate in a
filesystem scan to find or confirm a directory parent pointer. Create a
predicate that identifies such directories and abort the scrub.

Found by fuzzing xfs/1554 with multithreaded xfs_scrub enabled and
u3.bmx[0].startblock = zeroes.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 0d296634 Thu Aug 10 08:48:12 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: hide xfs_inode_is_allocated in scrub common code

This function is only used by online fsck, so let's move it there.
In the next patch, we'll fix it to work properly and to require that the
caller hold the AGI buffer locked. No major changes aside from
adjusting the signature a bit.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff 38bb1310 Tue Apr 11 20:00:22 MDT 2023 Darrick J. Wong <djwong@kernel.org> xfs: retain the AGI when we can't iget an inode to scrub the core

xchk_get_inode is not quite the right function to be calling from the
inode scrubber setup function. The common get_inode function either
gets an inode and installs it in the scrub context, or it returns an
error code explaining what happened. This is acceptable for most file
scrubbers because it is not in their scope to fix corruptions in the
inode core and fork areas that cause iget to fail.

Dealing with these problems is within the scope of the inode scrubber,
however. If iget fails with EFSCORRUPTED, we need to xchk_inode to flag
that as corruption. Since we can't get our hands on an incore inode, we
need to hold the AGI to prevent inode allocation activity so that
nothing changes in the inode metadata.

Looking ahead to the inode core repair patches, we will also need to
hold the AGI buffer into xrep_inode so that we can make modifications to
the xfs_dinode structure without any other thread swooping in to
allocate or free the inode.

Adapt the xchk_get_inode into xchk_setup_inode since this is a one-off
use case where the error codes we check for are a little different, and
the return state is much different from the common function.

xchk_setup_inode prepares to check or repair an inode record, so it must
continue the scrub operation even if the inode/inobt verifiers cause
xfs_iget to return EFSCORRUPTED. This is done by attaching the locked
AGI buffer to the scrub transaction and returning 0 to move on to the
actual scrub. (Later, the online inode repair code will also want the
xfs_imap structure so that it can reset the ondisk xfs_dinode
structure.)

xchk_get_inode retrieves an inode on behalf of a scrubber that operates
on an incore inode -- data/attr/cow forks, directories, xattrs,
symlinks, parent pointers, etc. If the inode/inobt verifiers fail and
xfs_iget returns EFSCORRUPTED, we want to exit to userspace (because the
caller should be fix the inode first) and drop everything we acquired
along the way.

A behavior common to both functions is that it's possible that xfs_scrub
asked for a scrub-by-handle concurrent with the inode being freed or the
passed-in inumber is invalid. In this case, we call xfs_imap to see if
the inobt index thinks the inode is allocated, and return ENOENT
("nothing to check here") to userspace if this is not the case. The
imap lookup is why both functions call xchk_iget_agi.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff ebd9027d Wed Aug 18 19:46:55 MDT 2021 Dave Chinner <dchinner@redhat.com> xfs: convert xfs_sb_version_has checks to use mount features

This is a conversion of the remaining xfs_sb_version_has..(sbp)
checks to use xfs_has_..(mp) feature checks.

This was largely done with a vim replacement macro that did:

:0,$s/xfs_sb_version_has\(.*\)&\(.*\)->m_sb/xfs_has_\1\2/g<CR>

A couple of other variants were also used, and the rest touched up
by hand.

$ size -t fs/xfs/built-in.a
text data bss dec hex filename
before 1127533 311352 484 1439369 15f689 (TOTALS)
after 1125360 311352 484 1437196 15ee0c (TOTALS)

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
/linux-master/fs/xfs/libxfs/
H A Dxfs_sb.cdiff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff de6077ec Thu Feb 22 01:31:03 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: report ag header corruption errors to the health tracking system

Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:

#!/bin/bash

# Detect missing calls to xfs_*_mark_sick

filter=cat
tty -s && filter=less

git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
H A Dxfs_sb.hdiff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 881f78f4 Mon Jan 29 21:27:23 MST 2024 Darrick J. Wong <djwong@kernel.org> xfs: remove conditional building of rt geometry validator functions

I mistakenly turned off CONFIG_XFS_RT in the Kconfig file for arm64
variant of the djwong-wtf git branch. Unfortunately, it took me a good
hour to figure out that RT wasn't built because this is what got printed
to dmesg:

XFS (sda2): realtime geometry sanity check failed
XFS (sda2): Metadata corruption detected at xfs_sb_read_verify+0x170/0x190 [xfs], xfs_sb block 0x0

Whereas I would have expected:

XFS (sda2): Not built with CONFIG_XFS_RT
XFS (sda2): RT mount failed

The root cause of these problems is the conditional compilation of the
new functions xfs_validate_rtextents and xfs_compute_rextslog that I
introduced in the two commits listed below. The !RT versions of these
functions return false and 0, respectively, which causes primary
superblock validation to fail, which explains the first message.

Move the two functions to other parts of libxfs that are not
conditionally defined by CONFIG_XFS_RT and remove the broken stubs so
that validation works again.

Fixes: e14293803f4e ("xfs: don't allow overly small or large realtime volumes")
Fixes: a6a38f309afc ("xfs: make rextslog computation consistent with mkfs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff 0b61f8a4 Tue Jun 05 20:42:14 MDT 2018 Dave Chinner <dchinner@redhat.com> xfs: convert to SPDX license tags

Remove the verbose license text from XFS files and replace them
with SPDX tags. This does not change the license of any of the code,
merely refers to the common, up-to-date license files in LICENSES/

This change was mostly scripted. fs/xfs/Makefile and
fs/xfs/libxfs/xfs_fs.h were modified by hand, the rest were detected
and modified by the following command:

for f in `git grep -l "GNU General" fs/xfs/` ; do
echo $f
cat $f | awk -f hdr.awk > $f.new
mv -f $f.new $f
done

And the hdr.awk script that did the modification (including
detecting the difference between GPL-2.0 and GPL-2.0+ licenses)
is as follows:

$ cat hdr.awk
BEGIN {
hdr = 1.0
tag = "GPL-2.0"
str = ""
}

/^ \* This program is free software/ {
hdr = 2.0;
next
}

/any later version./ {
tag = "GPL-2.0+"
next
}

/^ \*\// {
if (hdr > 0.0) {
print "// SPDX-License-Identifier: " tag
print str
print $0
str=""
hdr = 0.0
next
}
print $0
next
}

/^ \* / {
if (hdr > 1.0)
next
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
next
}

/^ \*/ {
if (hdr > 0.0)
next
print $0
next
}

// {
if (hdr > 0.0) {
if (str != "")
str = str "\n"
str = str $0
next
}
print $0
}

END { }
$

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Completed in 1388 milliseconds

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