radix tree: remove unused variable

Recent versions of clang warn about an unused variable, though older
versions saw the 'slot++' as a use and did not warn:

radix-tree.c:1136:50: error: parameter 'slot' set but not used [-Werror,-Wunused-but-set-parameter]

It's clearly not needed any more, so just remove it.

Link: https://lkml.kernel.org/r/20230811131023.2226509-1-arnd@kernel.org
Fixes: 3a08cd52c37c7 ("radix tree: Remove multiorder support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Rong Tao <rongtao@cestc.cn>
Cc: Tom Rix <trix@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

radix-tree: move declarations to header

The xarray.c file contains the only call to radix_tree_node_rcu_free(),
and it comes with its own extern declaration for it. This means the
function definition causes a missing-prototype warning:

lib/radix-tree.c:288:6: error: no previous prototype for 'radix_tree_node_rcu_free' [-Werror=missing-prototypes]

Instead, move the declaration for this function to a new header that can
be included by both, and do the same for the radix_tree_node_cachep
variable that has the same underlying problem but does not cause a warning
with gcc.

[zhangpeng.00@bytedance.com: fix building radix tree test suite]
Link: https://lkml.kernel.org/r/20230521095450.21332-1-zhangpeng.00@bytedance.com
Link: https://lkml.kernel.org/r/20230516194212.548910-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/radix-tree.c: fix uninitialized variable compilation warning

We need to set an initial value for offset to eliminate compilation
warning.

How to reproduce warning:

$ make -C tools/testing/radix-tree
radix-tree.c: In function `radix_tree_tag_clear':
radix-tree.c:1046:17: warning: `offset' may be used uninitialized in this function [-Wmaybe-uninitialized]
1046 | node_tag_clear(root, parent, tag, offset);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Link: https://lkml.kernel.org/r/tencent_DF74099967595DCEA93CBDC28D062026180A@qq.com
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/radix-tree: remove unused argument of insert_entries

insert_entries() doesn't use the 'bool replace' argument, and the function
is only used locally, remove the argument.

The historical context of the unused argument is as follow:

2: commit <3a08cd52c37c79> (radix tree: Remove multiorder support)
Remove the code related to macro CONFIG_RADIX_TREE_MULTIORDER
to convert to the xArray.
Without the macro, there is no need to retain the argument.

1: commit <175542f575723e> (radix-tree: add radix_tree_join)
Add insert_entries(..., bool replace) function, depending on the
macro CONFIG_RADIX_TREE_MULTIORDER definition, the implementation
is different. Notice that the implementation without the macro doesn't
use the argument.

[Matthew Wilcox: add historical context for argument]

Link: https://lkml.kernel.org/r/20220625135324.72574-1-wuchi.zero@gmail.com
Signed-off-by: wuchi <wuchi.zero@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib: remove "expecting prototype" kernel-doc warnings

Fix various kernel-doc warnings in lib/ due to missing or erroneous
function names.

Add kernel-doc for some function parameters that was missing. Use
kernel-doc "Return:" notation in earlycpio.c.

Quietens the following warnings:

lib/earlycpio.c:61: warning: expecting prototype for cpio_data find_cpio_data(). Prototype was for find_cpio_data() instead

lib/lru_cache.c:640: warning: expecting prototype for lc_dump(). Prototype was for lc_seq_dump_details() instead
lru_cache.c:90: warning: Function parameter or member 'cache' not described in 'lc_create'

lib/parman.c:368: warning: expecting prototype for parman_item_del(). Prototype was for parman_item_remove() instead
parman.c:309: warning: Excess function parameter 'prority' description in 'parman_prio_init'

lib/radix-tree.c:703: warning: expecting prototype for __radix_tree_insert(). Prototype was for radix_tree_insert() instead
radix-tree.c:180: warning: Excess function parameter 'addr' description in 'radix_tree_find_next_bit'
radix-tree.c:180: warning: Excess function parameter 'size' description in 'radix_tree_find_next_bit'
radix-tree.c:931: warning: Function parameter or member 'iter' not described in 'radix_tree_iter_replace'

Link: https://lkml.kernel.org/r/20210411221756.15461-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Jiri Pirko <jiri@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: delete duplicated words

Drop the repeated word "be".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200823040508.26086-1-rdunlap@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix tree test suite: Fix compilation

Introducing local_lock broke compilation; fix it all up.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

treewide: Remove uninitialized_var() usage

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
xargs perl -pi -e \
's/\buninitialized_var\(([^\)]+)\)/\1/g;
s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB
Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers
Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs
Signed-off-by: Kees Cook <keescook@chromium.org>

radix-tree: Use local_lock for protection

The radix-tree and idr preload mechanisms use preempt_disable() to protect
the complete operation between xxx_preload() and xxx_preload_end().

As the code inside the preempt disabled section acquires regular spinlocks,
which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and
eventually calls into a memory allocator, this conflicts with the RT
semantics.

Convert it to a local_lock which allows RT kernels to substitute them with
a real per CPU lock. On non RT kernels this maps to preempt_disable() as
before, but provides also lockdep coverage of the critical region.
No functional change.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200527201119.1692513-3-bigeasy@linutronix.de

ida: remove abandoned macros

3 IDA_ started macros aren't used from commit f32f004cddf8 ("ida: Convert
to XArray"). so better to remove them.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

idr: Fix idr_alloc_u32 on 32-bit systems

Attempting to allocate an entry at 0xffffffff when one is already
present would succeed in allocating one at 2^32, which would confuse
everything. Return -ENOSPC in this case, as expected.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 153

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 or at your option any
later version this program is distributed in the hope that it will
be useful but without any warranty without even the implied warranty
of merchantability or fitness for a particular purpose see the gnu
general public license for more details you should have received a
copy of the gnu general public license along with this program if
not write to the free software foundation inc 675 mass ave cambridge
ma 02139 usa

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 77 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.837555891@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

radix tree: Don't return retry entries from lookup

Commit 66ee620f06f9 ("idr: Permit any valid kernel pointer to be stored")
changed the radix tree lookup so that it stops when reaching the bottom
of the tree. However, the condition was added in the wrong place,
making it possible to return retry entries to the caller. Reorder the
tests to check for the retry entry before checking whether we're at the
bottom of the tree. The retry entry should never be found in the tree
root, so it's safe to defer the check until the end of the loop.

Add a regression test to the test-suite to be sure this doesn't come
back.

Fixes: 66ee620f06f9 ("idr: Permit any valid kernel pointer to be stored")
Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree: Remove multiorder support

All users have now been converted to the XArray. Removing the support
reduces code size and ensures new users will use the XArray instead.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree test suite: Convert tag_tagged_items to XArray

The tag_tagged_items() function is supposed to test the page-writeback
tagging code. Since that has been converted to the XArray, there's
not much point in testing the radix tree's tagging code. This requires
using the pthread mutex embedded in the xarray instead of an external
lock, so remove the pthread mutexes which protect xarrays/radix trees.
Also remove radix_tree_iter_tag_set() as this was the last user.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree: Remove radix_tree_clear_tags

The page cache was the only user of this interface and it has now
been converted to the XArray. Transform the test into a test of
xas_init_marks().

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree: Remove radix_tree_maybe_preload_order

This function was only used by the page cache which is now converted
to the XArray.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree: Remove split/join code

radix_tree_split and radix_tree_join were never used upstream. Remove
them; if they're needed in future they will be replaced by XArray
equivalents.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix tree: Remove radix_tree_update_node_t

The only user of this functionality was the workingset code, and it's
now been converted to the XArray. Remove __radix_tree_delete_node()
entirely as it was also only used by the workingset code.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

shmem: Convert shmem_alloc_hugepage to XArray

xa_find() is a slightly easier API to use than
radix_tree_gang_lookup_slot() because it contains its own RCU locking.
This commit removes the last user of radix_tree_gang_lookup_slot()
so remove the function too.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

page cache: Add and replace pages using the XArray

Use the XArray APIs to add and replace pages in the page cache. This
removes two uses of the radix tree preload API and is significantly
shorter code. It also removes the last user of __radix_tree_create()
outside radix-tree.c itself, so make it static.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

ida: Convert to XArray

Use the XA_TRACK_FREE ability to track which entries have a free bit,
similarly to how it uses the radix tree's IDR_FREE tag. This eliminates
the per-cpu ida_bitmap preload, and fixes the memory consumption
regression I introduced when making the IDR able to store any pointer.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

xarray: Add XArray unconditional store operations

xa_store() differs from radix_tree_insert() in that it will overwrite an
existing element in the array rather than returning an error. This is
the behaviour which most users want, and those that want more complex
behaviour generally want to use the xas family of routines anyway.

For memory allocation, xa_store() will first attempt to request memory
from the slab allocator; if memory is not immediately available, it will
drop the xa_lock and allocate memory, keeping a pointer in the xa_state.
It does not use the per-CPU cache, although those will continue to exist
until all radix tree users are converted to the xarray.

This patch also includes xa_erase() and __xa_erase() for a streamlined
way to store NULL. Since there is no need to allocate memory in order
to store a NULL in the XArray, we do not need to trouble the user with
deciding what memory allocation flags to use.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

xarray: Add XArray load operation

The xa_load function brings with it a lot of infrastructure; xa_empty(),
xa_is_err(), and large chunks of the XArray advanced API that are used
to implement xa_load.

As the test-suite demonstrates, it is possible to use the XArray functions
on a radix tree. The radix tree functions depend on the GFP flags being
stored in the root of the tree, so it's not possible to use the radix
tree functions on an XArray.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

xarray: Define struct xa_node

This is a direct replacement for struct radix_tree_node. A couple of
struct members have changed name, so convert those. Use a #define so
that radix tree users continue to work without change.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>

xarray: Add definition of struct xarray

This is a direct replacement for struct radix_tree_root. Some of the
struct members have changed name; convert those, and use a #define so
that radix_tree users continue to work without change.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>

xarray: Change definition of sibling entries

Instead of storing a pointer to the slot containing the canonical entry,
store the offset of the slot. Produces slightly more efficient code
(~300 bytes) and simplifies the implementation.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>

xarray: Replace exceptional entries

Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries. This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry). It is also a change in emphasis; exceptional entries are
intimidating and different. As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>

idr: Permit any valid kernel pointer to be stored

An upcoming change to the encoding of internal entries will set the bottom
two bits to 0b10. Unfortunately, m68k only aligns some data structures
to 2 bytes, so the IDR will interpret them as internal entries and things
will go badly wrong.

Change the radix tree so that it stops either when the node indicates
that it's the bottom of the tree (shift == 0) or when the entry is not an
internal entry. This means we cannot insert an arbitrary kernel pointer
as a multiorder entry, but the IDR does not permit multiorder entries.

Annoyingly, this means the IDR can no longer take advantage of the radix
tree's ability to store a single entry at offset 0 without allocating
memory. A pointer which is 2-byte aligned cannot be stored directly in
the root as it would be indistinguishable from a node, so we must allocate
a node in order to store a 2-byte pointer at index 0. The idr_replace()
function does not take a GFP flags argument, so cannot allocate memory.
If a user inserts a 4-byte aligned pointer at index 0 and then replaces
it with a 2-byte aligned pointer, we must be able to store it.

Arbitrary pointer values are still not permitted; pointers of the
form 2 + (i * 4) for values of i between 0 and 1023 are reserved for
the implementation. These are not valid kernel pointers as they would
point into the zero page.

This change does cause a runtime memory consumption regression for
the IDA. I will recover that later.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>

ida: Remove old API

Delete ida_pre_get(), ida_get_new(), ida_get_new_above() and ida_remove()
from the public API. Some of these functions still exist as internal
helpers, but they should not be called by consumers.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

radix-tree: Fix UBSAN warning

get_slot_offset() can be called with a NULL 'parent' argument.
In this case, the calculated value will not be used, but calculating
it is undefined. Rather than fixing the caller (__radix_tree_delete)
to not call get_slot_offset(), make get_slot_offset() robust against
being called with a NULL parent.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

idr: fix invalid ptr dereference on item delete

If the radix tree underlying the IDR happens to be full and we attempt
to remove an id which is larger than any id in the IDR, we will call
__radix_tree_delete() with an uninitialised 'slot' pointer, at which
point anything could happen. This was easiest to hit with a single
entry at id 0 and attempting to remove a non-0 id, but it could have
happened with 64 entries and attempting to remove an id >= 64.

Roman said:

The syzcaller test boils down to opening /dev/kvm, creating an
eventfd, and calling a couple of KVM ioctls. None of this requires
superuser. And the result is dereferencing an uninitialized pointer
which is likely a crash. The specific path caught by syzbot is via
KVM_HYPERV_EVENTD ioctl which is new in 4.17. But I guess there are
other user-triggerable paths, so cc:stable is probably justified.

Matthew added:

We have around 250 calls to idr_remove() in the kernel today. Many of
them pass an ID which is embedded in the object they're removing, so
they're safe. Picking a few likely candidates:

drivers/firewire/core-cdev.c looks unsafe; the ID comes from an ioctl.
drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c is similar
drivers/atm/nicstar.c could be taken down by a handcrafted packet

Link: http://lkml.kernel.org/r/20180518175025.GD6361@bombadil.infradead.org
Fixes: 0a835c4f090a ("Reimplement IDR and IDA using the radix tree")
Reported-by: <syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com>
Debugged-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix tree: fix multi-order iteration race

Fix a race in the multi-order iteration code which causes the kernel to
hit a GP fault. This was first seen with a production v4.15 based
kernel (4.15.6-300.fc27.x86_64) utilizing a DAX workload which used
order 9 PMD DAX entries.

The race has to do with how we tear down multi-order sibling entries
when we are removing an item from the tree. Remember for example that
an order 2 entry looks like this:

struct radix_tree_node.slots[] = [entry][sibling][sibling][sibling]

where 'entry' is in some slot in the struct radix_tree_node, and the
three slots following 'entry' contain sibling pointers which point back
to 'entry.'

When we delete 'entry' from the tree, we call :

radix_tree_delete()
radix_tree_delete_item()
__radix_tree_delete()
replace_slot()

replace_slot() first removes the siblings in order from the first to the
last, then at then replaces 'entry' with NULL. This means that for a
brief period of time we end up with one or more of the siblings removed,
so:

struct radix_tree_node.slots[] = [entry][NULL][sibling][sibling]

This causes an issue if you have a reader iterating over the slots in
the tree via radix_tree_for_each_slot() while only under
rcu_read_lock()/rcu_read_unlock() protection. This is a common case in
mm/filemap.c.

The issue is that when __radix_tree_next_slot() => skip_siblings() tries
to skip over the sibling entries in the slots, it currently does so with
an exact match on the slot directly preceding our current slot.
Normally this works:

V preceding slot
struct radix_tree_node.slots[] = [entry][sibling][sibling][sibling]
^ current slot

This lets you find the first sibling, and you skip them all in order.

But in the case where one of the siblings is NULL, that slot is skipped
and then our sibling detection is interrupted:

V preceding slot
struct radix_tree_node.slots[] = [entry][NULL][sibling][sibling]
^ current slot

This means that the sibling pointers aren't recognized since they point
all the way back to 'entry', so we think that they are normal internal
radix tree pointers. This causes us to think we need to walk down to a
struct radix_tree_node starting at the address of 'entry'.

In a real running kernel this will crash the thread with a GP fault when
you try and dereference the slots in your broken node starting at
'entry'.

We fix this race by fixing the way that skip_siblings() detects sibling
nodes. Instead of testing against the preceding slot we instead look
for siblings via is_sibling_entry() which compares against the position
of the struct radix_tree_node.slots[] array. This ensures that sibling
entries are properly identified, even if they are no longer contiguous
with the 'entry' they point to.

Link: http://lkml.kernel.org/r/20180503192430.7582-6-ross.zwisler@linux.intel.com
Fixes: 148deab223b2 ("radix-tree: improve multiorder iterators")
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: CR, Sapthagirish <sapthagirish.cr@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix tree: use GFP_ZONEMASK bits of gfp_t for flags

Patch series "XArray", v9. (First part thereof).

This patchset is, I believe, appropriate for merging for 4.17. It
contains the XArray implementation, to eventually replace the radix
tree, and converts the page cache to use it.

This conversion keeps the radix tree and XArray data structures in sync
at all times. That allows us to convert the page cache one function at
a time and should allow for easier bisection. Other than renaming some
elements of the structures, the data structures are fundamentally
unchanged; a radix tree walk and an XArray walk will touch the same
number of cachelines. I have changes planned to the XArray data
structure, but those will happen in future patches.

Improvements the XArray has over the radix tree:

- The radix tree provides operations like other trees do; 'insert' and
'delete'. But what most users really want is an automatically
resizing array, and so it makes more sense to give users an API that
is like an array -- 'load' and 'store'. We still have an 'insert'
operation for users that really want that semantic.

- The XArray considers locking as part of its API. This simplifies a
lot of users who formerly had to manage their own locking just for
the radix tree. It also improves code generation as we can now tell
RCU that we're holding a lock and it doesn't need to generate as much
fencing code. The other advantage is that tree nodes can be moved
(not yet implemented).

- GFP flags are now parameters to calls which may need to allocate
memory. The radix tree forced users to decide what the allocation
flags would be at creation time. It's much clearer to specify them at
allocation time.

- Memory is not preloaded; we don't tie up dozens of pages on the off
chance that the slab allocator fails. Instead, we drop the lock,
allocate a new node and retry the operation. We have to convert all
the radix tree, IDA and IDR preload users before we can realise this
benefit, but I have not yet found a user which cannot be converted.

- The XArray provides a cmpxchg operation. The radix tree forces users
to roll their own (and at least four have).

- Iterators take a 'max' parameter. That simplifies many users and will
reduce the amount of iteration done.

- Iteration can proceed backwards. We only have one user for this, but
since it's called as part of the pagefault readahead algorithm, that
seemed worth mentioning.

- RCU-protected pointers are not exposed as part of the API. There are
some fun bugs where the page cache forgets to use rcu_dereference()
in the current codebase.

- Value entries gain an extra bit compared to radix tree exceptional
entries. That gives us the extra bit we need to put huge page swap
entries in the page cache.

- Some iterators now take a 'filter' argument instead of having
separate iterators for tagged/untagged iterations.

The page cache is improved by this:

- Shorter, easier to read code

- More efficient iterations

- Reduction in size of struct address_space

- Fewer walks from the top of the data structure; the XArray API
encourages staying at the leaf node and conducting operations there.

This patch (of 8):

None of these bits may be used for slab allocations, so we can use them
as radix tree flags as long as we mask them off before passing them to
the slab allocator. Move the IDR flag from the high bits to the
GFP_ZONEMASK bits.

Link: http://lkml.kernel.org/r/20180313132639.17387-3-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ida: do zeroing in ida_pre_get()

As far as I can tell, the only place the per-cpu ida_bitmap is populated
is in ida_pre_get. The pre-allocated element is stolen in two places in
ida_get_new_above, in both cases immediately followed by a memset(0).

Since ida_get_new_above is called with locks held, do the zeroing in
ida_pre_get, or rather let kmalloc() do it. Also, apparently gcc
generates ~44 bytes of code to do a memset(, 0, 128):

$ scripts/bloat-o-meter vmlinux.{0,1}
add/remove: 0/0 grow/shrink: 2/1 up/down: 5/-88 (-83)
Function old new delta
ida_pre_get 115 119 +4
vermagic 27 28 +1
ida_get_new_above 715 627 -88

Link: http://lkml.kernel.org/r/20180108225634.15340-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Eric Biggers <ebiggers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

idr: Remove idr_alloc_ext

It has no more users, so remove it. Move idr_alloc() back into idr.c,
move the guts of idr_alloc_cmn() into idr_alloc_u32(), remove the
wrappers around idr_get_free_cmn() and rename it to idr_get_free().
While there is now no interface to allocate IDs larger than a u32,
the IDR internals remain ready to handle a larger ID should a need arise.

These changes make it possible to provide the guarantee that, if the
nextid pointer points into the object, the object's ID will be initialised
before a concurrent lookup can find the object.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

mm, truncate: do not check mapping for every page being truncated

During truncation, the mapping has already been checked for shmem and
dax so it's known that workingset_update_node is required.

This patch avoids the checks on mapping for each page being truncated.
In all other cases, a lookup helper is used to determine if
workingset_update_node() needs to be called. The one danger is that the
API is slightly harder to use as calling workingset_update_node directly
without checking for dax or shmem mappings could lead to surprises.
However, the API rarely needs to be used and hopefully the comment is
enough to give people the hint.

sparsetruncate (tiny)
4.14.0-rc4 4.14.0-rc4
oneirq-v1r1 pickhelper-v1r1
Min Time 141.00 ( 0.00%) 140.00 ( 0.71%)
1st-qrtle Time 142.00 ( 0.00%) 141.00 ( 0.70%)
2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%)
3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%)
Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%)
Max-95% Time 147.00 ( 0.00%) 145.00 ( 1.36%)
Max-99% Time 195.00 ( 0.00%) 191.00 ( 2.05%)
Max Time 230.00 ( 0.00%) 205.00 ( 10.87%)
Amean Time 144.37 ( 0.00%) 143.82 ( 0.38%)
Stddev Time 10.44 ( 0.00%) 9.00 ( 13.74%)
Coeff Time 7.23 ( 0.00%) 6.26 ( 13.41%)
Best99%Amean Time 143.72 ( 0.00%) 143.34 ( 0.26%)
Best95%Amean Time 142.37 ( 0.00%) 142.00 ( 0.26%)
Best90%Amean Time 142.19 ( 0.00%) 141.85 ( 0.24%)
Best75%Amean Time 141.92 ( 0.00%) 141.58 ( 0.24%)
Best50%Amean Time 141.69 ( 0.00%) 141.31 ( 0.27%)
Best25%Amean Time 141.38 ( 0.00%) 140.97 ( 0.29%)

As you'd expect, the gain is marginal but it can be detected. The
differences in bonnie are all within the noise which is not surprising
given the impact on the microbenchmark.

radix_tree_update_node_t is a callback for some radix operations that
optionally passes in a private field. The only user of the callback is
workingset_update_node and as it no longer requires a mapping, the
private field is removed.

Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: must check __radix_tree_preload() return value

__radix_tree_preload() only disables preemption if no error is returned.

So we really need to make sure callers always check the return value.

idr_preload() contract is to always disable preemption, so we need
to add a missing preempt_disable() if an error happened.

Similarly, ida_pre_get() only needs to call preempt_enable() in the
case no error happened.

Link: http://lkml.kernel.org/r/1504637190.15310.62.camel@edumazet-glaptop3.roam.corp.google.com
Fixes: 0a835c4f090a ("Reimplement IDR and IDA using the radix tree")
Fixes: 7ad3d4d85c7a ("ida: Move ida_bitmap to a percpu variable")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org> [4.11+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

idr: Add new APIs to support unsigned long

The following new APIs are added:

int idr_alloc_ext(struct idr *idr, void *ptr, unsigned long *index,
unsigned long start, unsigned long end, gfp_t gfp);
void *idr_remove_ext(struct idr *idr, unsigned long id);
void *idr_find_ext(const struct idr *idr, unsigned long id);
void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id);
void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);

Signed-off-by: Chris Mi <chrism@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drm/i915: Replace execbuf vma ht with an idr

This was the competing idea long ago, but it was only with the rewrite
of the idr as an radixtree and using the radixtree directly ourselves,
along with the realisation that we can store the vma directly in the
radixtree and only need a list for the reverse mapping, that made the
patch performant enough to displace using a hashtable. Though the vma ht
is fast and doesn't require any extra allocation (as we can embed the node
inside the vma), it does require a thread for resizing and serialization
and will have the occasional slow lookup. That is hairy enough to
investigate alternatives and favour them if equivalent in peak performance.
One advantage of allocating an indirection entry is that we can support a
single shared bo between many clients, something that was done on a
first-come first-serve basis for shared GGTT vma previously. To offset
the extra allocations, we create yet another kmem_cache for them.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170816085210.4199-5-chris@chris-wilson.co.uk

lockdep: allow to disable reclaim lockup detection

The current implementation of the reclaim lockup detection can lead to
false positives and those even happen and usually lead to tweak the code
to silence the lockdep by using GFP_NOFS even though the context can use
__GFP_FS just fine.

See

http://lkml.kernel.org/r/20160512080321.GA18496@dastard

as an example.

=================================
[ INFO: inconsistent lock state ]
4.5.0-rc2+ #4 Tainted: G O
---------------------------------
inconsistent {RECLAIM_FS-ON-R} -> {IN-RECLAIM_FS-W} usage.
kswapd0/543 [HC0[0]:SC0[0]:HE1:SE1] takes:

(&xfs_nondir_ilock_class){++++-+}, at: xfs_ilock+0x177/0x200 [xfs]

{RECLAIM_FS-ON-R} state was registered at:
mark_held_locks+0x79/0xa0
lockdep_trace_alloc+0xb3/0x100
kmem_cache_alloc+0x33/0x230
kmem_zone_alloc+0x81/0x120 [xfs]
xfs_refcountbt_init_cursor+0x3e/0xa0 [xfs]
__xfs_refcount_find_shared+0x75/0x580 [xfs]
xfs_refcount_find_shared+0x84/0xb0 [xfs]
xfs_getbmap+0x608/0x8c0 [xfs]
xfs_vn_fiemap+0xab/0xc0 [xfs]
do_vfs_ioctl+0x498/0x670
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x12/0x6f

CPU0
----
lock(&xfs_nondir_ilock_class);
<Interrupt>
lock(&xfs_nondir_ilock_class);

*** DEADLOCK ***

3 locks held by kswapd0/543:

stack backtrace:
CPU: 0 PID: 543 Comm: kswapd0 Tainted: G O 4.5.0-rc2+ #4
Call Trace:
lock_acquire+0xd8/0x1e0
down_write_nested+0x5e/0xc0
xfs_ilock+0x177/0x200 [xfs]
xfs_reflink_cancel_cow_range+0x150/0x300 [xfs]
xfs_fs_evict_inode+0xdc/0x1e0 [xfs]
evict+0xc5/0x190
dispose_list+0x39/0x60
prune_icache_sb+0x4b/0x60
super_cache_scan+0x14f/0x1a0
shrink_slab.part.63.constprop.79+0x1e9/0x4e0
shrink_zone+0x15e/0x170
kswapd+0x4f1/0xa80
kthread+0xf2/0x110
ret_from_fork+0x3f/0x70

To quote Dave:
"Ignoring whether reflink should be doing anything or not, that's a
"xfs_refcountbt_init_cursor() gets called both outside and inside
transactions" lockdep false positive case. The problem here is lockdep
has seen this allocation from within a transaction, hence a GFP_NOFS
allocation, and now it's seeing it in a GFP_KERNEL context. Also note
that we have an active reference to this inode.

So, because the reclaim annotations overload the interrupt level
detections and it's seen the inode ilock been taken in reclaim
("interrupt") context, this triggers a reclaim context warning where
it thinks it is unsafe to do this allocation in GFP_KERNEL context
holding the inode ilock..."

This sounds like a fundamental problem of the reclaim lock detection.
It is really impossible to annotate such a special usecase IMHO unless
the reclaim lockup detection is reworked completely. Until then it is
much better to provide a way to add "I know what I am doing flag" and
mark problematic places. This would prevent from abusing GFP_NOFS flag
which has a runtime effect even on configurations which have lockdep
disabled.

Introduce __GFP_NOLOCKDEP flag which tells the lockdep gfp tracking to
skip the current allocation request.

While we are at it also make sure that the radix tree doesn't
accidentaly override tags stored in the upper part of the gfp_mask.

Link: http://lkml.kernel.org/r/20170306131408.9828-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ida: Free correct IDA bitmap

There's a relatively rare race where we look at the per-cpu preallocated
IDA bitmap, see it's NULL, allocate a new one, and atomically update it.
If the kmalloc() happened to sleep and we were rescheduled to a different
CPU, or an interrupt came in at the exact right time, another task
might have successfully allocated a bitmap and already deposited it.
I forgot what the semantics of cmpxchg() were and ended up freeing the
wrong bitmap leading to KASAN reporting a use-after-free.

Dmitry found the bug with syzkaller & wrote the patch. I wrote the test
case that will reproduce the bug without his patch being applied.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: Fix __rcu annotations

Many places were missing __rcu annotations. A few places needed a few
lines of explanation about why it was safe to not use RCU accessors.
Add a custom CFLAGS setting to the Makefile to ensure that new patches
don't miss RCU annotations.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: Add rcu_dereference and rcu_assign_pointer calls

Some of these have been missing for many years. Others were recently
introduced by me. Fortunately, we have tools that help us find such
things.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix_tree_iter_resume: Fix out of bounds error

The address sanitizer occasionally finds an out of bounds error while
running the test-suite. It turned out to be a read of the pointer
immediately next to the tree root, but this out of bounds error could
have occurred elsewhere. This happens because radix_tree_iter_resume()
dereferences 'slot' before checking whether we've come to the end of
the chunk. We can just delete this line; the value was never used.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: Store a pointer to the root in each node

Instead of having this mysterious private_data in each radix_tree_node,
store a pointer to the root, which can be useful for debugging. This also
relieves the mm code from the duty of updating it.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: Chain preallocated nodes through ->parent

Chaining through the ->private_data member means we have to zero
->private_data after removing preallocated nodes from the list.
We're about to initialise ->parent anyway, so we can avoid zeroing it.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

ida: Use exceptional entries for small IDAs

We can use the root entry as a bitmap and save allocating a 128 byte
bitmap for an IDA that contains only a few entries (30 on a 32-bit
machine, 62 on a 64-bit machine). This costs about 300 bytes of kernel
text on x86-64, so as long as 3 IDAs fall into this category, this
is a net win for memory consumption.

Thanks to Rasmus Villemoes for his work documenting the problem and
collecting statistics on IDAs.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

ida: Move ida_bitmap to a percpu variable

When we preload the IDA, we allocate an IDA bitmap. Instead of storing
that preallocated bitmap in the IDA, we store it in a percpu variable.
Generally there are more IDAs in the system than CPUs, so this cuts down
on the number of preallocated bitmaps that are unused, and about half
of the IDA users did not call ida_destroy() so they were leaking IDA
bitmaps.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

Reimplement IDR and IDA using the radix tree

The IDR is very similar to the radix tree. It has some functionality that
the radix tree did not have (alloc next free, cyclic allocation, a
callback-based for_each, destroy tree), which is readily implementable on
top of the radix tree. A few small changes were needed in order to use a
tag to represent nodes with free space below them. More extensive
changes were needed to support storing NULL as a valid entry in an IDR.
Plain radix trees still interpret NULL as a not-present entry.

The IDA is reimplemented as a client of the newly enhanced radix tree. As
in the current implementation, it uses a bitmap at the last level of the
tree.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

radix-tree: Add radix_tree_iter_delete

Factor the deletion code out into __radix_tree_delete() and provide a
nice iterator-based wrapper around it. If we free the node, advance
the iterator to avoid reading from freed memory.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: Add radix_tree_iter_tag_clear()

The counterpart to radix_tree_iter_tag_set(), used by the IDR code

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Rehas Sachdeva <aquannie@gmail.com>

EXPORT_SYMBOL radix_tree_replace_slot

It will be used in drivers/md/raid5-cache.c

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

radix tree: constify some pointers

If we're just getting the value of a tag, or looking up an entry,
we won't modify the radix tree, so we can declare these functions as
taking a const pointer. Mostly for documentation purposes, though it
might help code generation.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>

radix-tree: fix private list warnings

The newly introduced warning in radix_tree_free_nodes() was testing the
wrong variable; it should have been 'old' instead of 'node'.

Fixes: ea07b862ac8e ("mm: workingset: fix use-after-free in shadow node shrinker")
Link: http://lkml.kernel.org/r/20170118163746.GA32495@cmpxchg.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: workingset: fix use-after-free in shadow node shrinker

Several people report seeing warnings about inconsistent radix tree
nodes followed by crashes in the workingset code, which all looked like
use-after-free access from the shadow node shrinker.

Dave Jones managed to reproduce the issue with a debug patch applied,
which confirmed that the radix tree shrinking indeed frees shadow nodes
while they are still linked to the shadow LRU:

WARNING: CPU: 2 PID: 53 at lib/radix-tree.c:643 delete_node+0x1e4/0x200
CPU: 2 PID: 53 Comm: kswapd0 Not tainted 4.10.0-rc2-think+ #3
Call Trace:
delete_node+0x1e4/0x200
__radix_tree_delete_node+0xd/0x10
shadow_lru_isolate+0xe6/0x220
__list_lru_walk_one.isra.4+0x9b/0x190
list_lru_walk_one+0x23/0x30
scan_shadow_nodes+0x2e/0x40
shrink_slab.part.44+0x23d/0x5d0
shrink_node+0x22c/0x330
kswapd+0x392/0x8f0

This is the WARN_ON_ONCE(!list_empty(&node->private_list)) placed in the
inlined radix_tree_shrink().

The problem is with 14b468791fa9 ("mm: workingset: move shadow entry
tracking to radix tree exceptional tracking"), which passes an update
callback into the radix tree to link and unlink shadow leaf nodes when
tree entries change, but forgot to pass the callback when reclaiming a
shadow node.

While the reclaimed shadow node itself is unlinked by the shrinker, its
deletion from the tree can cause the left-most leaf node in the tree to
be shrunk. If that happens to be a shadow node as well, we don't unlink
it from the LRU as we should.

Consider this tree, where the s are shadow entries:

root->rnode
|
[0 n]
| |
[s ] [sssss]

Now the shadow node shrinker reclaims the rightmost leaf node through
the shadow node LRU:

root->rnode
|
[0 ]
|
[s ]

Because the parent of the deleted node is the first level below the
root and has only one child in the left-most slot, the intermediate
level is shrunk and the node containing the single shadow is put in
its place:

root->rnode
|
[s ]

The shrinker again sees a single left-most slot in a first level node
and thus decides to store the shadow in root->rnode directly and free
the node - which is a leaf node on the shadow node LRU.

root->rnode
|
s

Without the update callback, the freed node remains on the shadow LRU,
where it causes later shrinker runs to crash.

Pass the node updater callback into __radix_tree_delete_node() in case
the deletion causes the left-most branch in the tree to collapse too.

Also add warnings when linked nodes are freed right away, rather than
wait for the use-after-free when the list is scanned much later.

Fixes: 14b468791fa9 ("mm: workingset: move shadow entry tracking to radix tree exceptional tracking")
Reported-by: Dave Chinner <david@fromorbit.com>
Reported-by: Hugh Dickins <hughd@google.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-and-tested-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chris Leech <cleech@redhat.com>
Cc: Lee Duncan <lduncan@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

redo: radix tree test suite: fix compilation

[ This resurrects commit 53855d10f456, which was reverted in
2b41226b39b6. It depended on commit d544abd5ff7d ("lib/radix-tree:
Convert to hotplug state machine") so now it is correct to apply ]

Patch "lib/radix-tree: Convert to hotplug state machine" breaks the test
suite as it adds a call to cpuhp_setup_state_nocalls() which is not
currently emulated in the test suite. Add it, and delete the emulation
of the old CPU hotplug mechanism.

Link: http://lkml.kernel.org/r/1480369871-5271-36-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: ensure counts are initialised

radix_tree_join() was freeing nodes with a non-zero ->exceptional count,
and radix_tree_split() wasn't zeroing ->exceptional when it allocated
the new node. Fix this by making all callers of radix_tree_node_alloc()
pass in the new counts (and some other always-initialised fields), which
will prevent the problem recurring if in future we decide to do
something similar.

Link: http://lkml.kernel.org/r/1481667692-14500-3-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix replacement for multiorder entries

When replacing an entry with NULL, we need to delete any sibling
entries. Also account deleting exceptional entries properly. Also fix
a bug with radix_tree_iter_replace() where we would fail to remove
entirely freed nodes. Also fix accounting bug when switching between
normal and exceptional entries with replace_slot. Also add testcases
for all these bugs.

Link: http://lkml.kernel.org/r/1480369871-5271-61-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add radix_tree_split_preload()

Calculate how many nodes we need to allocate to split an old_order entry
into multiple entries, each of size new_order. The test suite checks
that we allocated exactly the right number of nodes; neither too many
(checked by rtp->nr == 0), nor too few (checked by comparing
nr_allocated before and after the call to radix_tree_split()).

Link: http://lkml.kernel.org/r/1480369871-5271-60-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add radix_tree_split

This new function splits a larger multiorder entry into smaller entries
(potentially multi-order entries). These entries are initialised to
RADIX_TREE_RETRY to ensure that RCU walkers who see this state aren't
confused. The caller should then call radix_tree_for_each_slot() and
radix_tree_replace_slot() in order to turn these retry entries into the
intended new entries. Tags are replicated from the original multiorder
entry into each new entry.

Link: http://lkml.kernel.org/r/1480369871-5271-59-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add radix_tree_join

This new function allows for the replacement of many smaller entries in
the radix tree with one larger multiorder entry. From the point of view
of an RCU walker, they may see a mixture of the smaller entries and the
large entry during the same walk, but they will never see NULL for an
index which was populated before the join.

Link: http://lkml.kernel.org/r/1480369871-5271-58-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: delete radix_tree_range_tag_if_tagged()

This is an exceptionally complicated function with just one caller
(tag_pages_for_writeback). We devote a large portion of the runtime of
the test suite to testing this one function which has one caller. By
introducing the new function radix_tree_iter_tag_set(), we can eliminate
all of the complexity while keeping the performance. The caller can now
use a fairly standard radix_tree_for_each() loop, and it doesn't need to
worry about tricksy things like 'start' wrapping.

The test suite continues to spend a large amount of time investigating
this function, but now it's testing the underlying primitives such as
radix_tree_iter_resume() and the radix_tree_for_each_tagged() iterator
which are also used by other parts of the kernel.

Link: http://lkml.kernel.org/r/1480369871-5271-57-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: delete radix_tree_locate_item()

This rather complicated function can be better implemented as an
iterator. It has only one caller, so move the functionality to the only
place that needs it. Update the test suite to follow the same pattern.

Link: http://lkml.kernel.org/r/1480369871-5271-56-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Konstantin Khlebnikov <koct9i@gmail.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: improve multiorder iterators

This fixes several interlinked problems with the iterators in the
presence of multiorder entries.

1. radix_tree_iter_next() would only advance by one slot, which would
result in the iterators returning the same entry more than once if
there were sibling entries.

2. radix_tree_next_slot() could return an internal pointer instead of
a user pointer if a tagged multiorder entry was immediately followed by
an entry of lower order.

3. radix_tree_next_slot() expanded to a lot more code than it used to
when multiorder support was compiled in. And I wasn't comfortable with
entry_to_node() being in a header file.

Fixing radix_tree_iter_next() for the presence of sibling entries
necessarily involves examining the contents of the radix tree, so we now
need to pass 'slot' to radix_tree_iter_next(), and we need to change the
calling convention so it is called *before* dropping the lock which
protects the tree. Also rename it to radix_tree_iter_resume(), as some
people thought it was necessary to call radix_tree_iter_next() each time
around the loop.

radix_tree_next_slot() becomes closer to how it looked before multiorder
support was introduced. It only checks to see if the next entry in the
chunk is a sibling entry or a pointer to a node; this should be rare
enough that handling this case out of line is not a performance impact
(and such impact is amortised by the fact that the entry we just
processed was a multiorder entry). Also, radix_tree_next_slot() used to
force a new chunk lookup for untagged entries, which is more expensive
than the out of line sibling entry skipping.

Link: http://lkml.kernel.org/r/1480369871-5271-55-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: improve dump output

Print the indices of the entries as unsigned (instead of signed)
integers and print the parent node of each entry to help navigate around
larger trees where the layout is not quite so obvious. Print the
indices covered by a node. Rearrange the order of fields printed so the
indices and parents line up for each type of entry.

Link: http://lkml.kernel.org/r/1480369871-5271-53-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: make radix_tree_find_next_bit more useful

Since this function is specialised to the radix tree, pass in the node
and tag to calculate the address of the bitmap in
radix_tree_find_next_bit() instead of the caller. Likewise, there is no
need to pass in the size of the bitmap.

Link: http://lkml.kernel.org/r/1480369871-5271-52-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: create node_tag_set()

Similar to node_tag_clear(), factor node_tag_set() out of
radix_tree_range_tag_if_tagged().

Link: http://lkml.kernel.org/r/1480369871-5271-51-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: move rcu_head into a union with private_list

I want to be able to reference node->parent after freeing node.

Currently node->parent is in a union with rcu_head, so it is overwritten
when the node is put on the RCU list. We know that private_list is not
referenced after the node is freed, so it is safe for these two members
to share space.

Link: http://lkml.kernel.org/r/1480369871-5271-50-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix typo

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: workingset: move shadow entry tracking to radix tree exceptional tracking

Currently, we track the shadow entries in the page cache in the upper
bits of the radix_tree_node->count, behind the back of the radix tree
implementation. Because the radix tree code has no awareness of them,
we rely on random subtleties throughout the implementation (such as the
node->count != 1 check in the shrinking code, which is meant to exclude
multi-entry nodes but also happens to skip nodes with only one shadow
entry, as that's accounted in the upper bits). This is error prone and
has, in fact, caused the bug fixed in d3798ae8c6f3 ("mm: filemap: don't
plant shadow entries without radix tree node").

To remove these subtleties, this patch moves shadow entry tracking from
the upper bits of node->count to the existing counter for exceptional
entries. node->count goes back to being a simple counter of valid
entries in the tree node and can be shrunk to a single byte.

This vastly simplifies the page cache code. All accounting happens
natively inside the radix tree implementation, and maintaining the LRU
linkage of shadow nodes is consolidated into a single function in the
workingset code that is called for leaf nodes affected by a change in
the page cache tree.

This also removes the last user of the __radix_delete_node() return
value. Eliminate it.

Link: http://lkml.kernel.org/r/20161117193211.GE23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: update callback for changing leaf nodes

Support handing __radix_tree_replace() a callback that gets invoked for
all leaf nodes that change or get freed as a result of the slot
replacement, to assist users tracking nodes with node->private_list.

This prepares for putting page cache shadow entries into the radix tree
root again and drastically simplifying the shadow tracking.

Link: http://lkml.kernel.org/r/20161117193134.GD23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: add entry deletion support to __radix_tree_replace()

Page cache shadow entry handling will be a lot simpler when it can use a
single generic replacement function for pages, shadow entries, and
emptying slots.

Make __radix_tree_replace() properly account insertions and deletions in
node->count and garbage collect nodes as they become empty. Then
re-implement radix_tree_delete() on top of it.

Link: http://lkml.kernel.org/r/20161117193058.GC23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: check accounting of existing slot replacement users

The bug in khugepaged fixed earlier in this series shows that radix tree
slot replacement is fragile; and it will become more so when not only
NULL<->!NULL transitions need to be caught but transitions from and to
exceptional entries as well. We need checks.

Re-implement radix_tree_replace_slot() on top of the sanity-checked
__radix_tree_replace(). This requires existing callers to also pass the
radix tree root, but it'll warn us when somebody replaces slots with
contents that need proper accounting (transitions between NULL entries,
real entries, exceptional entries) and where a replacement through the
slot pointer would corrupt the radix tree node counts.

Link: http://lkml.kernel.org/r/20161117193021.GB23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: native accounting of exceptional entries

The way the page cache is sneaking shadow entries of evicted pages into
the radix tree past the node entry accounting and tracking them manually
in the upper bits of node->count is fraught with problems.

These shadow entries are marked in the tree as exceptional entries,
which are a native concept to the radix tree. Maintain an explicit
counter of exceptional entries in the radix tree node. Subsequent
patches will switch shadow entry tracking over to that counter.

DAX and shmem are the other users of exceptional entries. Since slot
replacements that change the entry type from regular to exceptional must
now be accounted, introduce a __radix_tree_replace() function that does
replacement and accounting, and switch DAX and shmem over.

The increase in radix tree node size is temporary. A followup patch
switches the shadow tracking to this new scheme and we'll no longer need
the upper bits in node->count and shrink that back to one byte.

Link: http://lkml.kernel.org/r/20161117192945.GA23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Revert "radix tree test suite: fix compilation"

This reverts commit 53855d10f4567a0577360b6448d52a863929775b.

It shouldn't have come in yet - it depends on the changes in linux-next
that will come in during the next merge window. As Matthew Wilcox says,
the test suite is broken with the current state without the revert.

Requested-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix tree test suite: fix compilation

Patch "lib/radix-tree: Convert to hotplug state machine" breaks the test
suite as it adds a call to cpuhp_setup_state_nocalls() which is not
currently emulated in the test suite. Add it, and delete the emulation
of the old CPU hotplug mechanism.

Link: http://lkml.kernel.org/r/1480369871-5271-36-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161103145021.28528-6-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

mm: filemap: don't plant shadow entries without radix tree node

When the underflow checks were added to workingset_node_shadow_dec(),
they triggered immediately:

kernel BUG at ./include/linux/swap.h:276!
invalid opcode: 0000 [#1] SMP
Modules linked in: isofs usb_storage fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_REJECT nf_reject_ipv6
soundcore wmi acpi_als pinctrl_sunrisepoint kfifo_buf tpm_tis industrialio acpi_pad pinctrl_intel tpm_tis_core tpm nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_crypt
CPU: 0 PID: 20929 Comm: blkid Not tainted 4.8.0-rc8-00087-gbe67d60ba944 #1
Hardware name: System manufacturer System Product Name/Z170-K, BIOS 1803 05/06/2016
task: ffff8faa93ecd940 task.stack: ffff8faa7f478000
RIP: page_cache_tree_insert+0xf1/0x100
Call Trace:
__add_to_page_cache_locked+0x12e/0x270
add_to_page_cache_lru+0x4e/0xe0
mpage_readpages+0x112/0x1d0
blkdev_readpages+0x1d/0x20
__do_page_cache_readahead+0x1ad/0x290
force_page_cache_readahead+0xaa/0x100
page_cache_sync_readahead+0x3f/0x50
generic_file_read_iter+0x5af/0x740
blkdev_read_iter+0x35/0x40
__vfs_read+0xe1/0x130
vfs_read+0x96/0x130
SyS_read+0x55/0xc0
entry_SYSCALL_64_fastpath+0x13/0x8f
Code: 03 00 48 8b 5d d8 65 48 33 1c 25 28 00 00 00 44 89 e8 75 19 48 83 c4 18 5b 41 5c 41 5d 41 5e 5d c3 0f 0b 41 bd ef ff ff ff eb d7 <0f> 0b e8 88 68 ef ff 0f 1f 84 00
RIP page_cache_tree_insert+0xf1/0x100

This is a long-standing bug in the way shadow entries are accounted in
the radix tree nodes. The shrinker needs to know when radix tree nodes
contain only shadow entries, no pages, so node->count is split in half
to count shadows in the upper bits and pages in the lower bits.

Unfortunately, the radix tree implementation doesn't know of this and
assumes all entries are in node->count. When there is a shadow entry
directly in root->rnode and the tree is later extended, the radix tree
implementation will copy that entry into the new node and and bump its
node->count, i.e. increases the page count bits. Once the shadow gets
removed and we subtract from the upper counter, node->count underflows
and triggers the warning. Afterwards, without node->count reaching 0
again, the radix tree node is leaked.

Limit shadow entries to when we have actual radix tree nodes and can
count them properly. That means we lose the ability to detect refaults
from files that had only the first page faulted in at eviction time.

Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-and-tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix tree: fix sibling entry handling in radix_tree_descend()

The fixes to the radix tree test suite show that the multi-order case is
broken. The basic reason is that the radix tree code uses tagged
pointers with the "internal" bit in the low bits, and calculating the
pointer indices was supposed to mask off those bits. But gcc will
notice that we then use the index to re-create the pointer, and will
avoid doing the arithmetic and use the tagged pointer directly.

This cleans the code up, using the existing is_sibling_entry() helper to
validate the sibling pointer range (instead of open-coding it), and
using entry_to_node() to mask off the low tag bit from the pointer. And
once you do that, you might as well just use the now cleaned-up pointer
directly.

[ Side note: the multi-order code isn't actually ever used in the kernel
right now, and the only reason I didn't just delete all that code is
that Kirill Shutemov piped up and said:

"Well, my ext4-with-huge-pages patchset[1] uses multi-order entries.
It also converts shmem-with-huge-pages and hugetlb to them.

I'm okay with converting it to other mechanism, but I need
something. (I looked into Konstantin's RFC patchset[2]. It looks
okay, but I don't feel myself qualified to review it as I don't
know much about radix-tree internals.)"

[1] http://lkml.kernel.org/r/20160915115523.29737-1-kirill.shutemov@linux.intel.com
[2] http://lkml.kernel.org/r/147230727479.9957.1087787722571077339.stgit@zurg ]

Reported-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Cedric Blancher <cedric.blancher@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: account nodes to memcg only if explicitly requested

Radix trees may be used not only for storing page cache pages, so
unconditionally accounting radix tree nodes to the current memory cgroup
is bad: if a radix tree node is used for storing data shared among
different cgroups we risk pinning dead memory cgroups forever.

So let's only account radix tree nodes if it was explicitly requested by
passing __GFP_ACCOUNT to INIT_RADIX_TREE. Currently, we only want to
account page cache entries, so mark mapping->page_tree so.

Fixes: 58e698af4c63 ("radix-tree: account radix_tree_node to memory cgroup")
Link: http://lkml.kernel.org/r/1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org> [4.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: implement radix_tree_maybe_preload_order()

The new helper is similar to radix_tree_maybe_preload(), but tries to
preload number of nodes required to insert (1 << order) continuous
naturally-aligned elements.

This is required to push huge pages into pagecache.

Link: http://lkml.kernel.org/r/1466021202-61880-24-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: make radix_tree_descend() more useful

Now that the shift amount is stored in the node, radix_tree_descend()
can calculate offset itself from index, which removes several lines of
code from each of the tree walkers.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: introduce radix_tree_replace_clear_tags()

In addition to replacing the entry, we also clear all associated tags.
This is really a one-off special for page_cache_tree_delete() which had
far too much detailed knowledge about how the radix tree works.

For efficiency, factor node_tag_clear() out of radix_tree_tag_clear() It
can be used by radix_tree_delete_item() as well as
radix_tree_replace_clear_tags().

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: tidy up __radix_tree_create()

1. Rename the existing variable 'slot' to 'child'.
2. Introduce a new variable called 'slot' which is the address of the
slot we're dealing with. This lets us simplify the tree insertion,
and removes the recalculation of 'slot' at the end of the function.
3. Using 'slot' in the sibling pointer insertion part makes the code
more readable.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: tidy up range_tag_if_tagged

Convert radix_tree_range_tag_if_tagged to name the nodes parent, node
and child instead of node & slot.

Use parent->offset instead of playing games with 'upindex'.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: tidy up next_chunk

Convert radix_tree_next_chunk to use 'child' instead of 'slot' as the
name of the child node. Also use node_maxindex() where it makes sense.

The 'rnode' variable was unnecessary; it doesn't overlap in usage with
'node', so we can just use 'node' the whole way through the function.

Improve the testcase to start the walk from every index in the carefully
constructed tree, and to accept any index within the range covered by
the entry.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: change naming conventions in radix_tree_shrink

Use the more standard 'node' and 'child' instead of 'to_free' and
'slot'.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rename radix_tree_is_indirect_ptr()

As with indirect_to_ptr(), ptr_to_indirect() and
RADIX_TREE_INDIRECT_PTR, change radix_tree_is_indirect_ptr() to
radix_tree_is_internal_node().

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rename indirect_to_ptr() to entry_to_node()

Mirrors the earlier commit introducing node_to_entry().

Also change the type returned to be a struct radix_tree_node pointer.
That lets us simplify a couple of places in the radix tree shrink &
extend paths where we could convert an entry into a pointer, modify the
node, then convert the pointer back into an entry.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rename ptr_to_indirect() to node_to_entry()

ptr_to_indirect() was a bad name. What it really means is "Convert this
pointer to a node into an entry suitable for storing in the radix tree".
So node_to_entry() seemed like a better name.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rename INDIRECT_PTR to INTERNAL_NODE

The name RADIX_TREE_INDIRECT_PTR doesn't really match the meaning.
RADIX_TREE_INTERNAL_NODE is a better name.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: remove root->height

The only remaining references to root->height were in extend and shrink,
where it was updated. Now we can remove it entirely.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: remove a use of root->height from delete_node

If radix_tree_shrink returns whether it managed to shrink, then
__radix_tree_delete_node doesn't ned to query the tree to find out
whether it did any work or not.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: replace node->height with node->shift

node->shift represents the shift necessary for looking in the slots
array at this level. It is equal to the old (node->height - 1) *
RADIX_TREE_MAP_SHIFT.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: split node->path into offset and height

Neither piece of information we're storing in node->path can be larger
than 64, so store each in its own unsigned char instead of shifting and
masking to store them both in an unsigned int.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: miscellaneous fixes

Typos, whitespace, grammar, line length, using the correct types, etc.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add copyright statements

The multiorder support is a sufficiently large feature to be worth
adding copyrigt lines for.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix radix_tree_dump() for multi-order entries

- Print which indices are covered by every leaf entry
- Print sibling entries
- Print the node pointer instead of the slot entry
- Build by default in userspace, and make it accessible to the test-suite

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix radix_tree_range_tag_if_tagged() for multiorder entries

I had previously decided that tagging a single multiorder entry would
count as tagging 2^order entries for the purposes of 'nr_to_tag'. I now
believe that decision to be a mistake, and it should count as a single
entry. That's more likely to be what callers expect.

When walking back up the tree from a newly-tagged entry, the current
code assumed we were starting from the lowest level of the tree; if we
have a multiorder entry with an order at least RADIX_TREE_MAP_SHIFT in
size then we need to shift the index by 'shift' before we start walking
back up the tree, or we will end up not setting tags on higher entries,
and then mistakenly thinking that entries below a certain point in the
tree are not tagged.

If the first index we examine is a sibling entry of a tagged multiorder
entry, we were not tagging it. We need to examine the canonical entry,
and the easiest way to do that is to use radix_tree_descend(). We then
have to skip over sibling slots when looking for the next entry in the
tree or we will end up walking back to the canonical entry.

Add several tests for radix_tree_range_tag_if_tagged().

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite radix_tree_locate_item

Use the new multi-order support functions to rewrite
radix_tree_locate_item(). Modify the locate tests to test multiorder
entries too.

[hughd@google.com: radix_tree_locate_item() is often returning the wrong index]
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1605012108490.1166@eggly.anvils
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix radix_tree_create for sibling entries

If the radix tree user attempted to insert a colliding entry with an
existing multiorder entry, then radix_tree_create() could encounter a
sibling entry when walking down the tree to look for a slot. Use
radix_tree_descend() to fix the problem, and add a test-case to make
sure the problem doesn't come back in future.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite radix_tree_tag_get

Use the new multi-order support functions to rewrite
radix_tree_tag_get()

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite radix_tree_tag_clear

Use the new multi-order support functions to rewrite
radix_tree_tag_clear()

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite radix_tree_tag_set

Use the new multi-order support functions to rewrite
radix_tree_tag_set()

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add support for multi-order iterating

This enables the macros radix_tree_for_each_slot() and friends to be
used with multi-order entries.

The way that this works is that we treat all entries in a given slots[]
array as a single chunk. If the index given to radix_tree_next_chunk()
happens to point us to a sibling entry, we will back up iter->index so
that it points to the canonical entry, and that will be the place where
we start our iteration.

As we're processing a chunk in radix_tree_next_slot(), we process
canonical entries, skip over sibling entries, and restart the chunk
lookup if we find a non-sibling indirect pointer. This drops back to
the radix_tree_next_chunk() code, which will re-walk the tree and look
for another chunk.

This allows us to properly handle multi-order entries mixed with other
entries that are at various heights in the radix tree.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix multiorder BUG_ON in radix_tree_insert

These BUG_ON tests are to ensure that all the tags are clear when
inserting a new entry. If we insert a multiorder entry, we'll end up
looking at the tags for a different node, and so the BUG_ON can end up
triggering spuriously.

Also, we now have three tags, not two, so check all three are clear, and
check all the root tags with a single call to BUG_ON since the bits are
stored contiguously.

Include a test-case to ensure this problem does not reoccur.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite __radix_tree_lookup

Use the new multi-order support functions to rewrite __radix_tree_lookup()

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix several shrinking bugs with multiorder entries

Setting the indirect bit on the user data entry used to be unambiguous
because the tree walking code knew not to expect internal nodes in the
last level of the tree. Multiorder entries can appear at any level of
the tree, and a leaf with the indirect bit set is indistinguishable from
a pointer to a node.

Introduce a special entry (RADIX_TREE_RETRY) which is neither a valid
user entry, nor a valid pointer to a node. The radix_tree_deref_retry()
function continues to work the same way, but tree walking code can
distinguish it from a pointer to a node.

Also fix the condition for setting slot->parent to NULL; it does not
matter what height the tree is, it only matters whether slot is an
indirect pointer. Move this code above the comment which is referring
to the assignment to root->rnode.

Also fix the condition for preventing the tree from shrinking to a
single entry if it's a multiorder entry.

Add a test-case to the test suite that checks that the tree goes back
down to its original height after an item is inserted & deleted from a
higher index in the tree.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix extending the tree for multi-order entries at offset 0

The current code will insert entries at each level, as if we're going to
add a new entry at the bottom level, so we then get an -EEXIST when we
try to insert the entry into the tree. The best way to fix this is to
not check 'order' when inserting into an empty tree.

We still need to 'extend' the tree to the height necessary for the maximum
index corresponding to this entry, so pass that value to
radix_tree_extend() rather than the index we're asked to create, or we
won't create a tree that's deep enough.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: introduce radix_tree_load_root()

All the tree walking functions start with some variant of this code;
centralise it in one place so we're not chasing subtly different bugs
everywhere.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: remove restriction on multi-order entries

Now that sibling pointers are handled explicitly, there is no purpose
served by restricting the order to be >= RADIX_TREE_MAP_SHIFT.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix deleting a multi-order entry through an alias

If we deleted an entry through an index which looked up a sibling
pointer, we'd end up zeroing out the wrong slots in the node. Use
get_slot_offset() to find the right slot.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix sibling entry insertion

The subtraction was the wrong way round, leading to undefined behaviour
(shift by an amount larger than the size of the type).

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add missing sibling entry functionality

The code I previously added to enable multiorder radix tree entries was
untested and therefore buggy. This commit adds the support functions
that Ross and I decided were necessary over a four-week period of
iterating various designs.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

raxix-tree: introduce CONFIG_RADIX_TREE_MULTIORDER

I've been receiving increasingly concerned notes from 0day about how
much my recent changes have been bloating the radix tree. Make it
happier by only including multiorder support if
CONFIG_TRANSPARENT_HUGEPAGES is set.

This is an independent Kconfig option, so other radix tree users can
also set it if they have a need.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: add radix_tree_dump

This is debug code which is #if 0 out.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: add support for multi-order entries

With huge pages, it is convenient to have the radix tree be able to
return an entry that covers multiple indices. Previous attempts to deal
with the problem have involved inserting N duplicate entries, which is a
waste of memory and leads to problems trying to handle aliased tags, or
probing the tree multiple times to find alternative entries which might
cover the requested index.

This approach inserts one canonical entry into the tree for a given
range of indices, and may also insert other entries in order to ensure
that lookups find the canonical entry.

This solution only tolerates inserting powers of two that are greater
than the fanout of the tree. If we wish to expand the radix tree's
abilities to support large-ish pages that is less than the fanout at the
penultimate level of the tree, then we would need to add one more step
in lookup to ensure that any sibling nodes in the final level of the
tree are dereferenced and we return the canonical entry that they
reference.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: loop based on shift count, not height

When we introduce entries that can cover multiple indices, we will need
to stop in __radix_tree_create based on the shift, not the height.
Split out for ease of bisect.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: tag all internal tree nodes as indirect pointers

Set the 'indirect_ptr' bit on all the pointers to internal nodes, not
just on the root node. This enables the following patches to support
multi-order entries in the radix tree. This patch is split out for ease
of bisection.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: account radix_tree_node to memory cgroup

Allocation of radix_tree_node objects can be easily triggered from
userspace, so we should account them to memory cgroup. Besides, we need
them accounted for making shadow node shrinker per memcg (see
mm/workingset.c).

A tricky thing about accounting radix_tree_node objects is that they are
mostly allocated through radix_tree_preload(), so we can't just set
SLAB_ACCOUNT for radix_tree_node_cachep - that would likely result in a
lot of unrelated cgroups using objects from each other's caches.

One way to overcome this would be making radix tree preloads per memcg,
but that would probably look cumbersome and overcomplicated.

Instead, we make radix_tree_node_alloc() first try to allocate from the
cache with __GFP_ACCOUNT, no matter if the caller has preloaded or not,
and only if it fails fall back on using per cpu preloads. This should
make most allocations accounted.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix race in gang lookup

If the indirect_ptr bit is set on a slot, that indicates we need to redo
the lookup. Introduce a new function radix_tree_iter_retry() which
forces the loop to retry the lookup by setting 'slot' to NULL and
turning the iterator back to point at the problematic entry.

This is a pretty rare problem to hit at the moment; the lookup has to
race with a grow of the radix tree from a height of 0. The consequences
of hitting this race are that gang lookup could return a pointer to a
radix_tree_node instead of a pointer to whatever the user had inserted
in the tree.

Fixes: cebbd29e1c2f ("radix-tree: rewrite gang lookup using iterator")
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd

__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts. They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve". __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".

Over time, callers had a requirement to not block when fallback options
were available. Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.

This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative. High priority users continue to use
__GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim. __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.

This patch then converts a number of sites

o __GFP_ATOMIC is used by callers that are high priority and have memory
pools for those requests. GFP_ATOMIC uses this flag.

o Callers that have a limited mempool to guarantee forward progress clear
__GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
into this category where kswapd will still be woken but atomic reserves
are not used as there is a one-entry mempool to guarantee progress.

o Callers that are checking if they are non-blocking should use the
helper gfpflags_allow_blocking() where possible. This is because
checking for __GFP_WAIT as was done historically now can trigger false
positives. Some exceptions like dm-crypt.c exist where the code intent
is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
flag manipulations.

o Callers that built their own GFP flags instead of starting with GFP_KERNEL
and friends now also need to specify __GFP_KSWAPD_RECLAIM.

The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.

The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL. They may
now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: replace preallocated node array with linked list

Currently we use per-cpu array to hold pointers to preallocated nodes.
Let's replace it with linked list. On x86_64 it saves 256 bytes in
per-cpu ELF section which may translate into freeing up 2MB of memory for
NR_CPUS==8192.

[akpm@linux-foundation.org: fix comment, coding style]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

sched/preempt: Merge preempt_mask.h into preempt.h

preempt_mask.h defines all the preempt_count semantics and related
symbols: preempt, softirq, hardirq, nmi, preempt active, need resched,
etc...

preempt.h defines the accessors and mutators of preempt_count.

But there is a messy dependency game around those two header files:

* preempt_mask.h includes preempt.h in order to access preempt_count()

* preempt_mask.h defines all preempt_count semantic and symbols
except PREEMPT_NEED_RESCHED that is needed by asm/preempt.h
Thus we need to define it from preempt.h, right before including
asm/preempt.h, instead of defining it to preempt_mask.h with the
other preempt_count symbols. Therefore the preempt_count semantics
happen to be spread out.

* We plan to introduce preempt_active_[enter,exit]() to consolidate
preempt_schedule*() code. But we'll need to access both preempt_count
mutators (preempt_count_add()) and preempt_count symbols
(PREEMPT_ACTIVE, PREEMPT_OFFSET). The usual place to define preempt
operations is in preempt.h but then we'll need symbols in
preempt_mask.h which already includes preempt.h. So we end up with
a ressource circle dependency.

Lets merge preempt_mask.h into preempt.h to solve these dependency issues.
This way we gather semantic symbols and operation definition of
preempt_count in a single file.

This is a dumb copy-paste merge. Further merge re-arrangments are
performed in a subsequent patch to ease review.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431441711-29753-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

lib/radix-tree.c: change to simpler include

The comment helpfully explains why hardirq.h is included, but since
commit 2d4b84739f0a ("hardirq: Split preempt count mask definitions")
in_interrupt() has been provided by preempt_mask.h. Use that instead,
saving around 40 lines in the generated dependency file.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations

Since radix_tree_preload() stack trace is not always useful for
debugging an actual radix tree memory leak, this patch updates the
kmemleak allocation stack trace in the radix_tree_node_alloc() function.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c: kernel-doc warning fix

index has been removed from __radix_tree_delete_node in 449dd6984d0e47
("mm: keep page cache radix tree nodes in check")

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: replace __get_cpu_var uses with this_cpu_ptr

Replace places where __get_cpu_var() is used for an address calculation
with this_cpu_ptr().

Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: keep page cache radix tree nodes in check

Previously, page cache radix tree nodes were freed after reclaim emptied
out their page pointers. But now reclaim stores shadow entries in their
place, which are only reclaimed when the inodes themselves are
reclaimed. This is problematic for bigger files that are still in use
after they have a significant amount of their cache reclaimed, without
any of those pages actually refaulting. The shadow entries will just
sit there and waste memory. In the worst case, the shadow entries will
accumulate until the machine runs out of memory.

To get this under control, the VM will track radix tree nodes
exclusively containing shadow entries on a per-NUMA node list. Per-NUMA
rather than global because we expect the radix tree nodes themselves to
be allocated node-locally and we want to reduce cross-node references of
otherwise independent cache workloads. A simple shrinker will then
reclaim these nodes on memory pressure.

A few things need to be stored in the radix tree node to implement the
shadow node LRU and allow tree deletions coming from the list:

1. There is no index available that would describe the reverse path
from the node up to the tree root, which is needed to perform a
deletion. To solve this, encode in each node its offset inside the
parent. This can be stored in the unused upper bits of the same
member that stores the node's height at no extra space cost.

2. The number of shadow entries needs to be counted in addition to the
regular entries, to quickly detect when the node is ready to go to
the shadow node LRU list. The current entry count is an unsigned
int but the maximum number of entries is 64, so a shadow counter
can easily be stored in the unused upper bits.

3. Tree modification needs tree lock and tree root, which are located
in the address space, so store an address_space backpointer in the
node. The parent pointer of the node is in a union with the 2-word
rcu_head, so the backpointer comes at no extra cost as well.

4. The node needs to be linked to an LRU list, which requires a list
head inside the node. This does increase the size of the node, but
it does not change the number of objects that fit into a slab page.

[akpm@linux-foundation.org: export the right function]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix_tree: tree node interface

Make struct radix_tree_node part of the public interface and provide API
functions to create, look up, and delete whole nodes. Refactor the
existing insert, look up, delete functions on top of these new node
primitives.

This will allow the VM to track and garbage collect page cache radix
tree nodes.

[sasha.levin@oracle.com: return correct error code on insertion failure]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: filemap: move radix tree hole searching here

The radix tree hole searching code is only used for page cache, for
example the readahead code trying to get a a picture of the area
surrounding a fault.

It sufficed to rely on the radix tree definition of holes, which is
"empty tree slot". But this is about to change, though, as shadow page
descriptors will be stored in the page cache after the actual pages get
evicted from memory.

Move the functions over to mm/filemap.c and make them native page cache
operations, where they can later be adapted to handle the new definition
of "page cache hole".

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix-tree: add radix_tree_delete_item()

Provide a function that does not just delete an entry at a given index,
but also allows passing in an expected item. Delete only if that item
is still located at the specified index.

This is handy when lockless tree traversals want to delete entries as
well because they don't have to do an second, locked lookup to verify
the slot has not changed under them before deleting the entry.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c: swapoff tmpfs radix_tree: remember to rcu_read_unlock

Running fsx on tmpfs with concurrent memhog-swapoff-swapon, lots of

BUG: sleeping function called from invalid context at kernel/fork.c:606
in_atomic(): 0, irqs_disabled(): 0, pid: 1394, name: swapoff
1 lock held by swapoff/1394:
#0: (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6

followed by

================================================
[ BUG: lock held when returning to user space! ]
3.14.0-rc1 #3 Not tainted
------------------------------------------------
swapoff/1394 is leaving the kernel with locks still held!
1 lock held by swapoff/1394:
#0: (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6

after which the system recovered nicely.

Whoops, I long ago forgot the rcu_read_unlock() on one unlikely branch.

Fixes e504f3fdd63d ("tmpfs radix_tree: locate_item to speed up swapoff")

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c: make radix_tree_node_alloc() work correctly within interrupt

With users of radix_tree_preload() run from interrupt (block/blk-ioc.c is
one such possible user), the following race can happen:

radix_tree_preload()
...
radix_tree_insert()
radix_tree_node_alloc()
if (rtp->nr) {
ret = rtp->nodes[rtp->nr - 1];
<interrupt>
...
radix_tree_preload()
...
radix_tree_insert()
radix_tree_node_alloc()
if (rtp->nr) {
ret = rtp->nodes[rtp->nr - 1];

And we give out one radix tree node twice. That clearly results in radix
tree corruption with different results (usually OOPS) depending on which
two users of radix tree race.

We fix the problem by making radix_tree_node_alloc() always allocate fresh
radix tree nodes when in interrupt. Using preloading when in interrupt
doesn't make sense since all the allocations have to be atomic anyway and
we cannot steal nodes from process-context users because some users rely
on radix_tree_insert() succeeding after radix_tree_preload().
in_interrupt() check is somewhat ugly but we cannot simply key off passed
gfp_mask as that is acquired from root_gfp_mask() and thus the same for
all preload users.

Another part of the fix is to avoid node preallocation in
radix_tree_preload() when passed gfp_mask doesn't allow waiting. Again,
preallocation in such case doesn't make sense and when preallocation would
happen in interrupt we could possibly leak some allocated nodes. However,
some users of radix_tree_preload() require following radix_tree_insert()
to succeed. To avoid unexpected effects for these users,
radix_tree_preload() only warns if passed gfp mask doesn't allow waiting
and we provide a new function radix_tree_maybe_preload() for those users
which get different gfp mask from different call sites and which are
prepared to handle radix_tree_insert() failure.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix contiguous iterator

This patch fixes bug in macro radix_tree_for_each_contig().

If radix_tree_next_slot() sees NULL in next slot it returns NULL, but following
radix_tree_next_chunk() switches iterating into next chunk. As result iterating
becomes non-contiguous and breaks vfs "splice" and all its users.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reported-and-bisected-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Reported-and-bisected-by: Ondrej Zary <linux@rainbow-software.org>
Reported-bisected-and-tested-by: Toralf Förster <toralf.foerster@gmx.de>
Link: https://lkml.org/lkml/2012/6/5/64
Cc: stable <stable@vger.kernel.org> # 3.4.x
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix preload vector size

We are not preallocating a sufficient number of nodes.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: rewrite gang lookup using iterator

Rewrite radix_tree_gang_lookup_* functions using the new radix-tree
iterator.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: introduce bit-optimized iterator

A series of radix tree cleanups, and usage of them in the core pagecache
code.

Micro-benchmark:

lookup 14 slots (typical page-vector size)
in radix-tree there earch <step> slot filled and tagged
before/after - nsec per full scan through tree

* Intel Sandy Bridge i7-2620M 4Mb L3
New code always faster

* AMD Athlon 6000+ 2x1Mb L2, without L3
New code generally faster,
Minor degradation (marked with "*") for huge sparse trees

* i386 on Sandy Bridge
New code faster for common cases: tagged and dense trees.
Some degradations for non-tagged lookup on sparse trees.

Ideally, there might help __ffs() analog for searching first non-zero
long element in array, gcc sometimes cannot optimize this loop corretly.

Numbers:

CPU: Intel Sandy Bridge i7-2620M 4Mb L3

radix-tree with 1024 slots:

tagged lookup

step 1 before 7156 after 3613
step 2 before 5399 after 2696
step 3 before 4779 after 1928
step 4 before 4456 after 1429
step 5 before 4292 after 1213
step 6 before 4183 after 1052
step 7 before 4157 after 951
step 8 before 4016 after 812
step 9 before 3952 after 851
step 10 before 3937 after 732
step 11 before 4023 after 709
step 12 before 3872 after 657
step 13 before 3892 after 633
step 14 before 3720 after 591
step 15 before 3879 after 578
step 16 before 3561 after 513

normal lookup

step 1 before 4266 after 3301
step 2 before 2695 after 2129
step 3 before 2083 after 1712
step 4 before 1801 after 1534
step 5 before 1628 after 1313
step 6 before 1551 after 1263
step 7 before 1475 after 1185
step 8 before 1432 after 1167
step 9 before 1373 after 1092
step 10 before 1339 after 1134
step 11 before 1292 after 1056
step 12 before 1319 after 1030
step 13 before 1276 after 1004
step 14 before 1256 after 987
step 15 before 1228 after 992
step 16 before 1247 after 999

radix-tree with 1024*1024*128 slots:

tagged lookup

step 1 before 1086102841 after 674196409
step 2 before 816839155 after 498138306
step 7 before 599728907 after 240676762
step 15 before 555729253 after 185219677
step 63 before 606637748 after 128585664
step 64 before 608384432 after 102945089
step 65 before 596987114 after 123996019
step 128 before 304459225 after 56783056
step 256 before 158846855 after 31232481
step 512 before 86085652 after 18950595
step 12345 before 6517189 after 1674057

normal lookup

step 1 before 626064869 after 544418266
step 2 before 418809975 after 336321473
step 7 before 242303598 after 207755560
step 15 before 208380563 after 176496355
step 63 before 186854206 after 167283638
step 64 before 176188060 after 170143976
step 65 before 185139608 after 167487116
step 128 before 88181865 after 86913490
step 256 before 45733628 after 45143534
step 512 before 24506038 after 23859036
step 12345 before 2177425 after 2018662

* AMD Athlon 6000+ 2x1Mb L2, without L3

radix-tree with 1024 slots:

tag-lookup

step 1 before 8164 after 5379
step 2 before 5818 after 5581
step 3 before 4959 after 4213
step 4 before 4371 after 3386
step 5 before 4204 after 2997
step 6 before 4950 after 2744
step 7 before 4598 after 2480
step 8 before 4251 after 2288
step 9 before 4262 after 2243
step 10 before 4175 after 2131
step 11 before 3999 after 2024
step 12 before 3979 after 1994
step 13 before 3842 after 1929
step 14 before 3750 after 1810
step 15 before 3735 after 1810
step 16 before 3532 after 1660

normal-lookup

step 1 before 7875 after 5847
step 2 before 4808 after 4071
step 3 before 4073 after 3462
step 4 before 3677 after 3074
step 5 before 4308 after 2978
step 6 before 3911 after 3807
step 7 before 3635 after 3522
step 8 before 3313 after 3202
step 9 before 3280 after 3257
step 10 before 3166 after 3083
step 11 before 3066 after 3026
step 12 before 2985 after 2982
step 13 before 2925 after 2924
step 14 before 2834 after 2808
step 15 before 2805 after 2803
step 16 before 2647 after 2622

radix-tree with 1024*1024*128 slots:

tag-lookup

step 1 before 1288059720 after 951736580
step 2 before 961292300 after 884212140
step 7 before 768905140 after 547267580
step 15 before 771319480 after 456550640
step 63 before 504847640 after 242704304
step 64 before 392484800 after 177920786
step 65 before 491162160 after 246895264
step 128 before 208084064 after 97348392
step 256 before 112401035 after 51408126
step 512 before 75825834 after 29145070
step 12345 before 5603166 after 2847330

normal-lookup

step 1 before 1025677120 after 861375100
step 2 before 647220080 after 572258540
step 7 before 505518960 after 484041813
step 15 before 430483053 after 444815320 *
step 63 before 388113453 after 404250546 *
step 64 before 374154666 after 396027440 *
step 65 before 381423973 after 396704853 *
step 128 before 190078700 after 202619384 *
step 256 before 100886756 after 102829108 *
step 512 before 64074505 after 56158720
step 12345 before 4237289 after 4422299 *

* i686 on Sandy bridge

radix-tree with 1024 slots:

tagged lookup

step 1 before 7990 after 4019
step 2 before 5698 after 2897
step 3 before 5013 after 2475
step 4 before 4630 after 1721
step 5 before 4346 after 1759
step 6 before 4299 after 1556
step 7 before 4098 after 1513
step 8 before 4115 after 1222
step 9 before 3983 after 1390
step 10 before 4077 after 1207
step 11 before 3921 after 1231
step 12 before 3894 after 1116
step 13 before 3840 after 1147
step 14 before 3799 after 1090
step 15 before 3797 after 1059
step 16 before 3783 after 745

normal lookup

step 1 before 5103 after 3499
step 2 before 3299 after 2550
step 3 before 2489 after 2370
step 4 before 2034 after 2302 *
step 5 before 1846 after 2268 *
step 6 before 1752 after 2249 *
step 7 before 1679 after 2164 *
step 8 before 1627 after 2153 *
step 9 before 1542 after 2095 *
step 10 before 1479 after 2109 *
step 11 before 1469 after 2009 *
step 12 before 1445 after 2039 *
step 13 before 1411 after 2013 *
step 14 before 1374 after 2046 *
step 15 before 1340 after 1975 *
step 16 before 1331 after 2000 *

radix-tree with 1024*1024*128 slots:

tagged lookup

step 1 before 1225865377 after 667153553
step 2 before 842427423 after 471533007
step 7 before 609296153 after 276260116
step 15 before 544232060 after 226859105
step 63 before 519209199 after 141343043
step 64 before 588980279 after 141951339
step 65 before 521099710 after 138282060
step 128 before 298476778 after 83390628
step 256 before 149358342 after 43602609
step 512 before 76994713 after 22911077
step 12345 before 5328666 after 1472111

normal lookup

step 1 before 819284564 after 533635310
step 2 before 512421605 after 364956155
step 7 before 271443305 after 305721345 *
step 15 before 223591630 after 273960216 *
step 63 before 190320247 after 217770207 *
step 64 before 178538168 after 267411372 *
step 65 before 186400423 after 215347937 *
step 128 before 88106045 after 140540612 *
step 256 before 44812420 after 70660377 *
step 512 before 24435438 after 36328275 *
step 12345 before 2123924 after 2148062 *

bloat-o-meter delta for this patchset + patchset with related shmem cleanups

bloat-o-meter: x86_64

add/remove: 4/3 grow/shrink: 5/6 up/down: 928/-939 (-11)
function old new delta
radix_tree_next_chunk - 499 +499
shmem_unuse 428 554 +126
shmem_radix_tree_replace 131 227 +96
find_get_pages_tag 354 419 +65
find_get_pages_contig 345 407 +62
find_get_pages 362 396 +34
__kstrtab_radix_tree_next_chunk - 22 +22
__ksymtab_radix_tree_next_chunk - 16 +16
__kcrctab_radix_tree_next_chunk - 8 +8
radix_tree_gang_lookup_slot 204 203 -1
static.shmem_xattr_set 384 381 -3
radix_tree_gang_lookup_tag_slot 208 191 -17
radix_tree_gang_lookup 231 187 -44
radix_tree_gang_lookup_tag 247 199 -48
shmem_unlock_mapping 278 190 -88
__lookup 217 - -217
__lookup_tag 242 - -242
radix_tree_locate_item 279 - -279

bloat-o-meter: i386

add/remove: 3/3 grow/shrink: 8/9 up/down: 1075/-1275 (-200)
function old new delta
radix_tree_next_chunk - 757 +757
shmem_unuse 352 449 +97
find_get_pages_contig 269 322 +53
shmem_radix_tree_replace 113 154 +41
find_get_pages_tag 277 318 +41
dcache_dir_lseek 426 458 +32
__kstrtab_radix_tree_next_chunk - 22 +22
vc_do_resize 968 977 +9
snd_pcm_lib_read1 725 733 +8
__ksymtab_radix_tree_next_chunk - 8 +8
netlbl_cipsov4_list 1120 1127 +7
find_get_pages 293 291 -2
new_slab 467 459 -8
bitfill_unaligned_rev 425 417 -8
radix_tree_gang_lookup_tag_slot 177 146 -31
blk_dump_cmd 267 229 -38
radix_tree_gang_lookup_slot 212 134 -78
shmem_unlock_mapping 221 128 -93
radix_tree_gang_lookup_tag 275 162 -113
radix_tree_gang_lookup 255 126 -129
__lookup 227 - -227
__lookup_tag 271 - -271
radix_tree_locate_item 277 - -277

This patch:

Implement a clean, simple and effective radix-tree iteration routine.

Iterating divided into two phases:
* lookup next chunk in radix-tree leaf node
* iterating through slots in this chunk

Main iterator function radix_tree_next_chunk() returns pointer to first
slot, and stores in the struct radix_tree_iter index of next-to-last slot.
For tagged-iterating it also constuct bitmask of tags for retunted chunk.
All additional logic implemented as static-inline functions and macroses.

Also adds radix_tree_find_next_bit() static-inline variant of
find_next_bit() optimized for small constant size arrays, because
find_next_bit() too heavy for searching in an array with one/two long
elements.

[akpm@linux-foundation.org: rework comments a bit]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: reduce the use of module.h wherever possible

For files only using THIS_MODULE and/or EXPORT_SYMBOL, map
them onto including export.h -- or if the file isn't even
using those, then just delete the include. Fix up any implicit
include dependencies that were being masked by module.h along
the way.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

radix_tree: take radix_tree_path off stack

Down, down in the deepest depths of GFP_NOIO page reclaim, we have
shrink_page_list() calling __remove_mapping() calling __delete_from_
swap_cache() or __delete_from_page_cache().

You would not expect those to need much stack, but in fact they call
radix_tree_delete(): which declares a 192-byte radix_tree_path array on
its stack (to record the node,offsets it visits when descending, in case
it needs to ascend to update them). And if any tag is still set [1],
that calls radix_tree_tag_clear(), which declares a further such
192-byte radix_tree_path array on the stack. (At least we have
interrupts disabled here, so won't then be pushing registers too.)

That was probably a good choice when most users were 32-bit (array of
half the size), and adding fields to radix_tree_node would have bloated
it unnecessarily. But nowadays many are 64-bit, and each
radix_tree_node contains a struct rcu_head, which is only used when
freeing; whereas the radix_tree_path info is only used for updating the
tree (deleting, clearing tags or setting tags if tagged) when a lock
must be held, of no interest when accessing the tree locklessly.

So add a parent pointer to the radix_tree_node, in union with the
rcu_head, and remove all uses of the radix_tree_path. There would be
space in that union to save the offset when descending as before (we can
argue that a lock must already be held to exclude other users), but
recalculating it when ascending is both easy (a constant shift and a
constant mask) and uncommon, so it seems better just to do that.

Two little optimizations: no need to decrement height when descending,
adjusting shift is enough; and once radix_tree_tag_if_tagged() has set
tag on a node and its ancestors, it need not ascend from that node
again.

perf on the radix tree test harness reports radix_tree_insert() as 2%
slower (now having to set parent), but radix_tree_delete() 24% faster.
Surely that's an exaggeration from rtth's artificially low map shift 3,
but forcing it back to 6 still rates radix_tree_delete() 8% faster.

[1] Can a pagecache tag (dirty, writeback or towrite) actually still be
set at the time of radix_tree_delete()? Perhaps not if the filesystem is
well-behaved. But although I've not tracked any stack overflow down to
this cause, I have observed a curious case in which a dirty tag is set
and left set on tmpfs: page migration's migrate_page_copy() happens to
use __set_page_dirty_nobuffers() to set PageDirty on the newpage, and
that sets PAGECACHE_TAG_DIRTY as a side-effect - harmless to a
filesystem which doesn't use tags, except for this stack depth issue.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Nai Xia <nai.xia@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: clean away saw_unset_tag leftovers

radix_tree_tag_get()'s BUG (when it sees a tag after saw_unset_tag) was
unsafe and removed in 2.6.34, but the pointless saw_unset_tag left behind.

Remove it now, and return 0 as soon as we see unset tag - we already rely
upon the root tag to be correct, returning 0 immediately if it's not set.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tmpfs radix_tree: locate_item to speed up swapoff

We have already acknowledged that swapoff of a tmpfs file is slower than
it was before conversion to the generic radix_tree: a little slower
there will be acceptable, if the hotter paths are faster.

But it was a shock to find swapoff of a 500MB file 20 times slower on my
laptop, taking 10 minutes; and at that rate it significantly slows down
my testing.

Now, most of that turned out to be overhead from PROVE_LOCKING and
PROVE_RCU: without those it was only 4 times slower than before; and
more realistic tests on other machines don't fare as badly.

I've tried a number of things to improve it, including tagging the swap
entries, then doing lookup by tag: I'd expected that to halve the time,
but in practice it's erratic, and often counter-productive.

The only change I've so far found to make a consistent improvement, is
to short-circuit the way we go back and forth, gang lookup packing
entries into the array supplied, then shmem scanning that array for the
target entry. Scanning in place doubles the speed, so it's now only
twice as slow as before (or three times slower when the PROVEs are on).

So, add radix_tree_locate_item() as an expedient, once-off,
single-caller hack to do the lookup directly in place. #ifdef it on
CONFIG_SHMEM and CONFIG_SWAP, as much to document its limited
applicability as save space in other configurations. And, sadly,
#include sched.h for cond_resched().

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: exceptional entries and indices

A patchset to extend tmpfs to MAX_LFS_FILESIZE by abandoning its
peculiar swap vector, instead keeping a file's swap entries in the same
radix tree as its struct page pointers: thus saving memory, and
simplifying its code and locking.

This patch:

The radix_tree is used by several subsystems for different purposes. A
major use is to store the struct page pointers of a file's pagecache for
memory management. But what if mm wanted to store something other than
page pointers there too?

The low bit of a radix_tree entry is already used to denote an indirect
pointer, for internal use, and the unlikely radix_tree_deref_retry()
case.

Define the next bit as denoting an exceptional entry, and supply inline
functions radix_tree_exception() to return non-0 in either unlikely
case, and radix_tree_exceptional_entry() to return non-0 in the second
case.

If a subsystem already uses radix_tree with that bit set, no problem: it
does not affect internal workings at all, but is defined for the
convenience of those storing well-aligned pointers in the radix_tree.

The radix_tree_gang_lookups have an implicit assumption that the caller
can deduce the offset of each entry returned e.g. by the page->index of
a struct page. But that may not be feasible for some kinds of item to
be stored there.

radix_tree_gang_lookup_slot() allow for an optional indices argument,
output array in which to return those offsets. The same could be added
to other radix_tree_gang_lookups, but for now keep it to the only one
for which we need it.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree: radix_tree_gang_lookup_tag_slot() may never return

Executed command: fsstress -d /mnt -n 600 -p 850

crash> bt
PID: 7947 TASK: ffff880160546a70 CPU: 0 COMMAND: "fsstress"
#0 [ffff8800dfc07d00] machine_kexec at ffffffff81030db9
#1 [ffff8800dfc07d70] crash_kexec at ffffffff810a7952
#2 [ffff8800dfc07e40] oops_end at ffffffff814aa7c8
#3 [ffff8800dfc07e70] die_nmi at ffffffff814aa969
#4 [ffff8800dfc07ea0] do_nmi_callback at ffffffff8102b07b
#5 [ffff8800dfc07f10] do_nmi at ffffffff814aa514
#6 [ffff8800dfc07f50] nmi at ffffffff814a9d60
[exception RIP: __lookup_tag+100]
RIP: ffffffff812274b4 RSP: ffff88016056b998 RFLAGS: 00000287
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000006
RDX: 000000000000001d RSI: ffff88016056bb18 RDI: ffff8800c85366e0
RBP: ffff88016056b9c8 R8: ffff88016056b9e8 R9: 0000000000000000
R10: 000000000000000e R11: ffff8800c8536908 R12: 0000000000000010
R13: 0000000000000040 R14: ffffffffffffffc0 R15: ffff8800c85366e0
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
<NMI exception stack>
#7 [ffff88016056b998] __lookup_tag at ffffffff812274b4
#8 [ffff88016056b9d0] radix_tree_gang_lookup_tag_slot at ffffffff81227605
#9 [ffff88016056ba20] find_get_pages_tag at ffffffff810fc110
#10 [ffff88016056ba80] pagevec_lookup_tag at ffffffff81105e85
#11 [ffff88016056baa0] write_cache_pages at ffffffff81104c47
#12 [ffff88016056bbd0] generic_writepages at ffffffff81105014
#13 [ffff88016056bbe0] do_writepages at ffffffff81105055
#14 [ffff88016056bbf0] __filemap_fdatawrite_range at ffffffff810fb2cb
#15 [ffff88016056bc40] filemap_write_and_wait_range at ffffffff810fb32a
#16 [ffff88016056bc70] generic_file_direct_write at ffffffff810fb3dc
#17 [ffff88016056bce0] __generic_file_aio_write at ffffffff810fcee5
#18 [ffff88016056bda0] generic_file_aio_write at ffffffff810fd085
#19 [ffff88016056bdf0] do_sync_write at ffffffff8114f9ea
#20 [ffff88016056bf00] vfs_write at ffffffff8114fcf8
#21 [ffff88016056bf30] sys_write at ffffffff81150691
#22 [ffff88016056bf80] system_call_fastpath at ffffffff8100c0b2

I think this root cause is the following:

radix_tree_range_tag_if_tagged() always tags the root tag with settag
if the root tag is set with iftag even if there are no iftag tags
in the specified range (Of course, there are some iftag tags
outside the specified range).

===============================================================================
[[[Detailed description]]]

(1) Why cannot radix_tree_gang_lookup_tag_slot() return forever?

__lookup_tag():
- Return with 0.
- Return with the index which is not bigger than the old one as the
input parameter.

Therefore the following "while" repeats forever because the above
conditions cause "ret" not to be updated and the cur_index cannot be
changed into the bigger one.

(So, radix_tree_gang_lookup_tag_slot() cannot return forever.)

radix_tree_gang_lookup_tag_slot():
1178 while (ret < max_items) {
1179 unsigned int slots_found;
1180 unsigned long next_index; /* Index of next search */
1181
1182 if (cur_index > max_index)
1183 break;
1184 slots_found = __lookup_tag(node, results + ret,
1185 cur_index, max_items - ret, &next_index,
tag);
1186 ret += slots_found;
// cannot update ret because slots_found == 0.
// so, this while loops forever.
1187 if (next_index == 0)
1188 break;
1189 cur_index = next_index;
1190 }

(2) Why does __lookup_tag() return with 0 and doesn't update the index?

Assuming the following:
- the one of the slot in radix_tree_node is NULL.
- the one of the tag which corresponds to the slot sets with
PAGECACHE_TAG_TOWRITE or other.
- In a certain height(!=0), the corresponding index is 0.

a) __lookup_tag() notices that the tag is set.

1005 static unsigned int
1006 __lookup_tag(struct radix_tree_node *slot, void ***results, unsigned long index,
1007 unsigned int max_items, unsigned long *next_index, unsigned int tag)
1008 {
1009 unsigned int nr_found = 0;
1010 unsigned int shift, height;
1011
1012 height = slot->height;
1013 if (height == 0)
1014 goto out;
1015 shift = (height-1) * RADIX_TREE_MAP_SHIFT;
1016
1017 while (height > 0) {
1018 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
1019
1020 for (;;) {
1021 if (tag_get(slot, tag, i))
1022 break;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* the index is not updated yet.

b) __lookup_tag() notices that the slot is NULL.

1023 index &= ~((1UL << shift) - 1);
1024 index += 1UL << shift;
1025 if (index == 0)
1026 goto out; /* 32-bit wraparound */
1027 i++;
1028 if (i == RADIX_TREE_MAP_SIZE)
1029 goto out;
1030 }
1031 height--;
1032 if (height == 0) { /* Bottom level: grab some items */
...
1055 }
1056 shift -= RADIX_TREE_MAP_SHIFT;
1057 slot = rcu_dereference_raw(slot->slots[i]);
1058 if (slot == NULL)
1059 break;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

c) __lookup_tag() doesn't update the index and return with 0.

1060 }
1061 out:
1062 *next_index = index;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1063 return nr_found;
1064 }

(3) Why is the slot NULL even if the tag is set?

Because radix_tree_range_tag_if_tagged() always sets the root tag with
PAGECACHE_TAG_TOWRITE if the root tag is set with PAGECACHE_TAG_DIRTY,
even if there is no tag which can be set with PAGECACHE_TAG_TOWRITE
in the specified range (from *first_indexp to last_index). Of course,
some PAGECACHE_TAG_DIRTY nodes must exist outside the specified range.
(radix_tree_range_tag_if_tagged() is called only from tag_pages_for_writeback())

640 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root
*root,
641 unsigned long *first_indexp, unsigned long last_index,
642 unsigned long nr_to_tag,
643 unsigned int iftag, unsigned int settag)
644 {
645 unsigned int height = root->height;
646 struct radix_tree_path path[height];
647 struct radix_tree_path *pathp = path;
648 struct radix_tree_node *slot;
649 unsigned int shift;
650 unsigned long tagged = 0;
651 unsigned long index = *first_indexp;
652
653 last_index = min(last_index, radix_tree_maxindex(height));
654 if (index > last_index)
655 return 0;
656 if (!nr_to_tag)
657 return 0;
658 if (!root_tag_get(root, iftag)) {
659 *first_indexp = last_index + 1;
660 return 0;
661 }
662 if (height == 0) {
663 *first_indexp = last_index + 1;
664 root_tag_set(root, settag);
665 return 1;
666 }
...
733 root_tag_set(root, settag);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
734 *first_indexp = index;
735
736 return tagged;
737 }

As the result, there is no radix_tree_node which is set with
PAGECACHE_TAG_TOWRITE but the root tag(radix_tree_root) is set with
PAGECACHE_TAG_TOWRITE.

[figure: inside radix_tree]
(Please see the figure with typewriter font)
===========================================
[roottag = DIRTY]
| tag=0:NOTHING
tag[0 0 0 1] 1:DIRTY
[x x x +] 2:WRITEBACK
| 3:DIRTY,WRITEBACK
p 4:TOWRITE
<---> 5:DIRTY,TOWRITE ...
specified range (index: 0 to 2)

* There is no DIRTY tag within the specified range.
(But there is a DIRTY tag outside that range.)

| | | | | | | | |
after calling tag_pages_for_writeback()
| | | | | | | | |
v v v v v v v v v

[roottag = DIRTY,TOWRITE]
| p is "page".
tag[0 0 0 1] x is NULL.
[x x x +] +- is a pointer to "page".
|
p

* But TOWRITE tag is set on the root tag.
============================================

After that, radix_tree_extend() via radix_tree_insert() is called
when the page is added.
This function sets the new radix_tree_node with PAGECACHE_TAG_TOWRITE
to succeed the status of the root tag.

246 static int radix_tree_extend(struct radix_tree_root *root, unsigned long
index)
247 {
248 struct radix_tree_node *node;
249 unsigned int height;
250 int tag;
251
252 /* Figure out what the height should be. */
253 height = root->height + 1;
254 while (index > radix_tree_maxindex(height))
255 height++;
256
257 if (root->rnode == NULL) {
258 root->height = height;
259 goto out;
260 }
261
262 do {
263 unsigned int newheight;
264 if (!(node = radix_tree_node_alloc(root)))
265 return -ENOMEM;
266
267 /* Increase the height. */
268 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
269
270 /* Propagate the aggregated tag info into the new root */
271 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
272 if (root_tag_get(root, tag))
273 tag_set(node, tag, 0);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
274 }

===========================================
[roottag = DIRTY,TOWRITE]
| :
tag[0 0 0 1] [0 0 0 0]
[x x x +] [+ x x x]
| |
p p (new page)

| | | | | | | | |
after calling radix_tree_insert
| | | | | | | | |
v v v v v v v v v

[roottag = DIRTY,TOWRITE]
|
tag [5 0 0 0] * DIRTY and TOWRITE tags are
[+ + x x] succeeded to the new node.
| |
tag [0 0 0 1] [0 0 0 0]
[x x x +] [+ x x x]
| |
p p
============================================

After that, the index 3 page is released by remove_from_page_cache().
Then we can make the situation that the tag is set with PAGECACHE_TAG_TOWRITE
and that the slot which corresponds to the tag is NULL.
===========================================
[roottag = DIRTY,TOWRITE]
|
tag [5 0 0 0]
[+ + x x]
| |
tag [0 0 0 1] [0 0 0 0]
[x x x +] [+ x x x]
| |
p p
(remove)

| | | | | | | | |
after calling remove_page_cache
| | | | | | | | |
v v v v v v v v v

[roottag = DIRTY,TOWRITE]
|
tag [4 0 0 0] * Only DIRTY tag is cleared
[x + x x] because no TOWRITE tag is existed
| in the bottom node.
[0 0 0 0]
[+ x x x]
|
p
============================================

To solve this problem

Change to that radix_tree_tag_if_tagged() doesn't tag the root tag
if it doesn't set any tags within the specified range.

Like this.
============================================
640 unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root
*root,
641 unsigned long *first_indexp, unsigned long last_index,
642 unsigned long nr_to_tag,
643 unsigned int iftag, unsigned int settag)
644 {
650 unsigned long tagged = 0;
...
733 if (tagged)
^^^^^^^^^^^^^^^^^^^^^^^^
734 root_tag_set(root, settag);
735 *first_indexp = index;
736
737 return tagged;
738 }

============================================

Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix RCU bug

Salman Qazi describes the following radix-tree bug:

In the following case, we get can get a deadlock:

0. The radix tree contains two items, one has the index 0.
1. The reader (in this case find_get_pages) takes the rcu_read_lock.
2. The reader acquires slot(s) for item(s) including the index 0 item.
3. The non-zero index item is deleted, and as a consequence the other item is
moved to the root of the tree. The place where it used to be is queued for
deletion after the readers finish.
3b. The zero item is deleted, removing it from the direct slot, it remains in
the rcu-delayed indirect node.
4. The reader looks at the index 0 slot, and finds that the page has 0 ref
count
5. The reader looks at it again, hoping that the item will either be freed or
the ref count will increase. This never happens, as the slot it is looking
at will never be updated. Also, this slot can never be reclaimed because
the reader is holding rcu_read_lock and is in an infinite loop.

The fix is to re-use the same "indirect" pointer case that requires a slot
lookup retry into a general "retry the lookup" bit.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Reported-by: Salman Qazi <sqazi@google.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: radix_tree_range_tag_if_tagged() can set incorrect tags

Commit ebf8aa44beed48cd17893a83d92a4403e5f9d9e2 ("radix-tree:
omplement function radix_tree_range_tag_if_tagged") does not safely
set tags on on intermediate tree nodes. The code walks down the tree
setting tags before it has fully resolved the path to the leaf under
the assumption there will be a leaf slot with the tag set in the
range it is searching.

Unfortunately, this is not a valid assumption - we can abort after
setting a tag on an intermediate node if we overrun the number of
tags we are allowed to set in a batch, or stop scanning because we
we have passed the last scan index before we reach a leaf slot with
the tag we are searching for set.

As a result, we can leave the function with tags set on intemediate
nodes which can be tripped over later by tag-based lookups. The
result of these stale tags is that lookup may end prematurely or
livelock because the lookup cannot make progress.

The fix for the problem involves reocrding the traversal path we
take to the leaf nodes, and only propagating the tags back up the
tree once the tag is set in the leaf node slot. We are already
recording the path for efficient traversal, so there is no
additional overhead to do the intermediately node tag setting in
this manner.

This fixes a radix tree lookup livelock triggered by the new
writeback sync livelock avoidance code introduced in commit
f446daaea9d4a420d16c606f755f3689dcb2d0ce ("mm: implement writeback
livelock avoidance using page tagging").

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Acked-by: Jan Kara <jack@suse.cz>

radix-tree: clear all tags in radix_tree_node_rcu_free

Commit f446daaea9d4a420d16c606f755f3689dcb2d0ce ("mm: implement
writeback livelock avoidance using page tagging") introduced a new
radix tree tag, increasing the number of tags in each node from 2 to
3. It did not, however, fix up the code in
radix_tree_node_rcu_free() that cleans up after radix_tree_shrink()
and hence could leave stray tags set in the new tag array.

The result is that the livelock avoidance code added in the the
above commit would hit stale tags when doing tag based lookups,
resulting in livelocks when trying to traverse the tree.

Fix this problem in radix_tree_node_rcu_free() so it doesn't happen
again in the future by using a loop to walk all the tags up to
RADIX_TREE_MAX_TAGS to clear the stray tags radix_tree_shrink()
leaves behind.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Acked-by: Nick Piggin <npiggin@kernel.dk>
Acked-by: Jan Kara <jack@suse.cz>

lib/radix-tree.c: fix overflow in radix_tree_range_tag_if_tagged()

When radix_tree_maxindex() is ~0UL, it can happen that scanning overflows
index and tree traversal code goes astray reading memory until it hits
unreadable memory. Check for overflow and exit in that case.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: __rcu annotations

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Nick Piggin <npiggin@suse.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

radix-tree: omplement function radix_tree_range_tag_if_tagged

Implement function for setting one tag if another tag is set for each item
in given range.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix radix_tree_prev_hole() underflow case

radix_tree_prev_hole() used LONG_MAX to detect underflow; however,
ULONG_MAX is clearly what was intended, both here and by its only user
(count_history_pages at mm/readahead.c).

Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix_tree_tag_get() is not as safe as the docs make out [ver #2]

radix_tree_tag_get() is not safe to use concurrently with radix_tree_tag_set()
or radix_tree_tag_clear(). The problem is that the double tag_get() in
radix_tree_tag_get():

if (!tag_get(node, tag, offset))
saw_unset_tag = 1;
if (height == 1) {
int ret = tag_get(node, tag, offset);

may see the value change due to the action of set/clear. RCU is no protection
against this as no pointers are being changed, no nodes are being replaced
according to a COW protocol - set/clear alter the node directly.

The documentation in linux/radix-tree.h, however, says that
radix_tree_tag_get() is an exception to the rule that "any function modifying
the tree or tags (...) must exclude other modifications, and exclude any
functions reading the tree".

The problem is that the next statement in radix_tree_tag_get() checks that the
tag doesn't vary over time:

BUG_ON(ret && saw_unset_tag);

This has been seen happening in FS-Cache:

https://www.redhat.com/archives/linux-cachefs/2010-April/msg00013.html

To this end, remove the BUG_ON() from radix_tree_tag_get() and note in various
comments that the value of the tag may change whilst the RCU read lock is held,
and thus that the return value of radix_tree_tag_get() may not be relied upon
unless radix_tree_tag_set/clear() and radix_tree_delete() are excluded from
running concurrently with it.

Reported-by: Romain DEGEZ <romain.degez@smartjog.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.

2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).

* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

radix-tree: Disable RCU lockdep checking in radix tree

Because the radix tree is used with many different locking
designs, we cannot do any effective checking without changing
the radix-tree APIs. It might make sense to do this later, but
only if the RCU lockdep checking proves itself sufficiently
valuable.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-10-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

FS-Cache: Don't delete pending pages from the page-store tracking tree

Don't delete pending pages from the page-store tracking tree, but rather send
them for another write as they've presumably been updated.

Signed-off-by: David Howells <dhowells@redhat.com>

FS-Cache: Use radix tree preload correctly in tracking of pages to be stored

__fscache_write_page() attempts to load the radix tree preallocation pool for
the CPU it is on before calling radix_tree_insert(), as the insertion must be
done inside a pair of spinlocks.

Use of the preallocation pool, however, is contingent on the radix tree being
initialised without __GFP_WAIT specified. __fscache_acquire_cookie() was
passing GFP_NOFS to INIT_RADIX_TREE() - but that includes __GFP_WAIT.

The solution is to AND out __GFP_WAIT.

Additionally, the banner comment to radix_tree_preload() is altered to make
note of this prerequisite. Possibly there should be a WARN_ON() too.

Without this fix, I have seen the following recursive deadlock caused by
radix_tree_insert() attempting to allocate memory inside the spinlocked
region, which resulted in FS-Cache being called back into to release memory -
which required the spinlock already held.

=============================================
[ INFO: possible recursive locking detected ]
2.6.32-rc6-cachefs #24
---------------------------------------------
nfsiod/7916 is trying to acquire lock:
(&cookie->lock){+.+.-.}, at: [<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache]

but task is already holding lock:
(&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache]

other info that might help us debug this:
5 locks held by nfsiod/7916:
#0: (nfsiod){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2
#1: (&task->u.tk_work#2){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2
#2: (&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache]
#3: (&object->lock#2){+.+.-.}, at: [<ffffffffa0076b07>] __fscache_write_page+0x197/0x3f3 [fscache]
#4: (&cookie->stores_lock){+.+...}, at: [<ffffffffa0076b0f>] __fscache_write_page+0x19f/0x3f3 [fscache]

stack backtrace:
Pid: 7916, comm: nfsiod Not tainted 2.6.32-rc6-cachefs #24
Call Trace:
[<ffffffff8105ac7f>] __lock_acquire+0x1649/0x16e3
[<ffffffff81059ded>] ? __lock_acquire+0x7b7/0x16e3
[<ffffffff8100e27d>] ? dump_trace+0x248/0x257
[<ffffffff8105ad70>] lock_acquire+0x57/0x6d
[<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffff8135467c>] _spin_lock+0x2c/0x3b
[<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffffa0077eb7>] ? __fscache_check_page_write+0x0/0x71 [fscache]
[<ffffffffa00b4755>] nfs_fscache_release_page+0x86/0xc4 [nfs]
[<ffffffffa00907f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff81087ffb>] try_to_release_page+0x32/0x3b
[<ffffffff81092c2b>] shrink_page_list+0x316/0x4ac
[<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70
[<ffffffff8135451b>] ? _spin_unlock_irq+0x2b/0x31
[<ffffffff81093153>] shrink_inactive_list+0x392/0x67c
[<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70
[<ffffffff810934ca>] shrink_list+0x8d/0x8f
[<ffffffff81093744>] shrink_zone+0x278/0x33c
[<ffffffff81052c70>] ? ktime_get_ts+0xad/0xba
[<ffffffff8109453b>] try_to_free_pages+0x22e/0x392
[<ffffffff8109184c>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e16b>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff810ae24a>] cache_alloc_refill+0x34d/0x6c1
[<ffffffff811bcf74>] ? radix_tree_node_alloc+0x52/0x5c
[<ffffffff810ae929>] kmem_cache_alloc+0xb2/0x118
[<ffffffff811bcf74>] radix_tree_node_alloc+0x52/0x5c
[<ffffffff811bcfd5>] radix_tree_insert+0x57/0x19c
[<ffffffffa0076b53>] __fscache_write_page+0x1e3/0x3f3 [fscache]
[<ffffffffa00b4248>] __nfs_readpage_to_fscache+0x58/0x11e [nfs]
[<ffffffffa009bb77>] nfs_readpage_release+0x34/0x9b [nfs]
[<ffffffffa009c0d9>] nfs_readpage_release_full+0x32/0x4b [nfs]
[<ffffffffa0006cff>] rpc_release_calldata+0x12/0x14 [sunrpc]
[<ffffffffa0006e2d>] rpc_free_task+0x59/0x61 [sunrpc]
[<ffffffffa0006f03>] rpc_async_release+0x10/0x12 [sunrpc]
[<ffffffff810482e5>] worker_thread+0x1ef/0x2e2
[<ffffffff81048290>] ? worker_thread+0x19a/0x2e2
[<ffffffff81352433>] ? thread_return+0x3e/0x101
[<ffffffffa0006ef3>] ? rpc_async_release+0x0/0x12 [sunrpc]
[<ffffffff8104bff5>] ? autoremove_wake_function+0x0/0x34
[<ffffffff81058d25>] ? trace_hardirqs_on+0xd/0xf
[<ffffffff810480f6>] ? worker_thread+0x0/0x2e2
[<ffffffff8104bd21>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8104c2b9>] ? add_wait_queue+0x15/0x44
[<ffffffff8104bca7>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20

Signed-off-by: David Howells <dhowells@redhat.com>

lib: do code optimization for radix_tree_lookup() and radix_tree_lookup_slot()

radix_tree_lookup() and radix_tree_lookup_slot() have much the
same code except for the return value.

Introduce radix_tree_lookup_element() to do the real work.

/*
* is_slot == 1 : search for the slot.
* is_slot == 0 : search for the node.
*/
static void * radix_tree_lookup_element(struct radix_tree_root *root,
unsigned long index, int is_slot);

Signed-off-by: Huang Shijie <shijie8@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add radix_tree_prev_hole()

The counterpart of radix_tree_next_hole(). To be used by context readahead.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Vladislav Bolkhovitin <vst@vlnb.net>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: radix_tree.c make percpu variable static

radix_tree_preloads is unused outside of this file, make it static.

Noticed by sparse:
lib/radix-tree.c:84:1: warning: symbol 'per_cpu__radix_tree_preloads' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

trivial: radix-tree: document wrap-around issue of radix_tree_next_hole()

And some 80-line cleanups.

Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

SL*B: drop kmem cache argument from constructor

Kmem cache passed to constructor is only needed for constructors that are
themselves multiplexeres. Nobody uses this "feature", nor does anybody uses
passed kmem cache in non-trivial way, so pass only pointer to object.

Non-trivial places are:
arch/powerpc/mm/init_64.c
arch/powerpc/mm/hugetlbpage.c

This is flag day, yes.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Jon Tollefson <kniht@linux.vnet.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Matt Mackall <mpm@selenic.com>
[akpm@linux-foundation.org: fix arch/powerpc/mm/hugetlbpage.c]
[akpm@linux-foundation.org: fix mm/slab.c]
[akpm@linux-foundation.org: fix ubifs]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: add gang_lookup_slot, gang_lookup_slot_tag

Introduce gang_lookup_slot() and gang_lookup_slot_tag() functions, which
are used by lockless pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Christoph has moved

Remove all clameter@sgi.com addresses from the kernel tree since they will
become invalid on June 27th. Change my maintainer email address for the
slab allocators to cl@linux-foundation.org (which will be the new email
address for the future).

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: fix small lockless radix-tree bug

We shrink a radix tree when its root node has only one child, in the left
most slot. The child becomes the new root node. To perform this
operation in a manner compatible with concurrent lockless lookups, we
atomically switch the root pointer from the parent to its child.

However a concurrent lockless lookup may now have loaded a pointer to the
parent (and is presently deciding what to do next). For this reason, we
also have to keep the parent node in a valid state after shrinking the
tree, until the next RCU grace period -- otherwise this lookup with the
parent pointer may not do the right thing. Notably, we need to keep the
child in the left most slot there in case that is requested by the lookup.

This is all pretty standard RCU stuff. It is worth repeating because in
my eagerness to obey the radix tree node constructor scheme, I had broken
it by zeroing the radix tree node before the grace period.

What could happen is that a lookup can load the parent pointer, then
decide it wants to follow the left most child slot, only to find the slot
contained NULL due to the concurrent shrinker having zeroed the parent
node before waiting for a grace period. The lookup would return a false
negative as a result.

Fix it by doing that clearing in the RCU callback. I would normally want
to rip out the constructor entirely, but radix tree nodes are one of those
places where they make sense (only few cachelines will be touched soon
after allocation).

This was never actually found in any lockless pagecache testing or by the
test harness, but by seeing the odd problem with my scalable vmap rewrite.
I have not tickled the test harness into reproducing it yet, but I'll
keep working at it.

Fortunately, it is not a problem anywhere lockless pagecache is used in
mainline kernels (pagecache probe is not a guarantee, and brd does not
have concurrent lookups and deletes).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Remove set_migrateflags()

Migrate flags must be set on slab creation as agreed upon when the antifrag
logic was reviewed. Otherwise some slabs of a slabcache will end up in the
unmovable and others in the reclaimable section depending on which flag was
active when a new slab page was allocated.

This likely slid in somehow when antifrag was merged. Remove it.

The buffer_heads are always allocated with __GFP_RECLAIMABLE because the
SLAB_RECLAIM_ACCOUNT option is set. The set_migrateflags() never had any
effect there.

Radix tree allocations are not directly reclaimable but they are allocated
with __GFP_RECLAIMABLE set on each allocation. We now set
SLAB_RECLAIM_ACCOUNT on radix tree slab creation making sure that radix
tree slabs are consistently placed in the reclaimable section. Radix tree
slabs will also be accounted as such.

There is then no user left of set_migratepages. So remove it.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: avoid atomic allocations for preloaded insertions

Most pagecache (and some other) radix tree insertions have the great
opportunity to preallocate a few nodes with relaxed gfp flags. But the
preallocation is squandered when it comes time to allocate a node, we
default to first attempting a GFP_ATOMIC allocation -- that doesn't
normally fail, but it can eat into atomic memory reserves that we don't
need to be using.

Another upshot of this is that it removes the sometimes highly contended
zone->lock from underneath tree_lock. Pagecache insertions are always
performed with a radix tree preload, and after this change, such a
situation will never fall back to kmem_cache_alloc within
radix_tree_node_alloc.

David Miller reports seeing this allocation fail on a highly threaded
sparc64 system:

[527319.459981] dd: page allocation failure. order:0, mode:0x20
[527319.460403] Call Trace:
[527319.460568] [00000000004b71e0] __slab_alloc+0x1b0/0x6a8
[527319.460636] [00000000004b7bbc] kmem_cache_alloc+0x4c/0xa8
[527319.460698] [000000000055309c] radix_tree_node_alloc+0x20/0x90
[527319.460763] [0000000000553238] radix_tree_insert+0x12c/0x260
[527319.460830] [0000000000495cd0] add_to_page_cache+0x38/0xb0
[527319.460893] [00000000004e4794] mpage_readpages+0x6c/0x134
[527319.460955] [000000000049c7fc] __do_page_cache_readahead+0x170/0x280
[527319.461028] [000000000049cc88] ondemand_readahead+0x208/0x214
[527319.461094] [0000000000496018] do_generic_mapping_read+0xe8/0x428
[527319.461152] [0000000000497948] generic_file_aio_read+0x108/0x170
[527319.461217] [00000000004badac] do_sync_read+0x88/0xd0
[527319.461292] [00000000004bb5cc] vfs_read+0x78/0x10c
[527319.461361] [00000000004bb920] sys_read+0x34/0x60
[527319.461424] [0000000000406294] linux_sparc_syscall32+0x3c/0x40

The calltrace is significant: __do_page_cache_readahead allocates a number
of pages with GFP_KERNEL, and hence it should have reclaimed sufficient
memory to satisfy GFP_ATOMIC allocations. However after the list of pages
goes to mpage_readpages, there can be significant intervals (including disk
IO) before all the pages are inserted into the radix-tree. So the reserves
can easily be depleted at that point. The patch is confirmed to fix the
problem.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

avoid negative (and full-width) shifts in radix-tree.c

Negative shifts are not allowed in C (the result is undefined). Same thing
with full-width shifts.

It works on most platforms but not on the VAX with gcc 4.0.1 (it results in an
"operand reserved" fault).

Shifting by more than the width of the value on the left is also not
allowed. I think the extra '>> 1' tacked on at the end in the original
code was an attempt to work around that. Getting rid of that is an extra
feature of this patch.

Here's the chapter and verse, taken from the final draft of the C99
standard ("6.5.7 Bitwise shift operators", paragraph 3):

"The integer promotions are performed on each of the operands. The
type of the result is that of the promoted left operand. If the
value of the right operand is negative or is greater than or equal
to the width of the promoted left operand, the behavior is
undefined."

Thank you to Jan-Benedict Glaw, Christoph Hellwig, Maciej Rozycki, Pekka
Enberg, Andreas Schwab, and Christoph Lameter for review. Special thanks
to Andreas for spotting that my fix only removed half the undefined
behaviour.

Signed-off-by: Peter Lund <firefly@vax64.dk>
Christoph Lameter <clameter@sgi.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Andreas Schwab <schwab@suse.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: WU Fengguang <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Slab API: remove useless ctor parameter and reorder parameters

Slab constructors currently have a flags parameter that is never used. And
the order of the arguments is opposite to other slab functions. The object
pointer is placed before the kmem_cache pointer.

Convert

ctor(void *object, struct kmem_cache *s, unsigned long flags)

to

ctor(struct kmem_cache *s, void *object)

throughout the kernel

[akpm@linux-foundation.org: coupla fixes]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Group short-lived and reclaimable kernel allocations

This patch marks a number of allocations that are either short-lived such as
network buffers or are reclaimable such as inode allocations. When something
like updatedb is called, long-lived and unmovable kernel allocations tend to
be spread throughout the address space which increases fragmentation.

This patch groups these allocations together as much as possible by adding a
new MIGRATE_TYPE. The MIGRATE_RECLAIMABLE type is for allocations that can be
reclaimed on demand, but not moved. i.e. they can be migrated by deleting
them and re-reading the information from elsewhere.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fix the max path calculation in radix-tree.c

A while back, Nick Piggin introduced a patch to reduce the node memory
usage for small files (commit cfd9b7df4abd3257c9e381b0e445817b26a51c0c):

-#define RADIX_TREE_MAP_SHIFT 6
+#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)

Unfortunately, he didn't take into account the fact that the
calculation of the maximum path was based on an assumption of having
to round up:

#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)

So, if CONFIG_BASE_SMALL is set, you will end up with a
RADIX_TREE_MAX_PATH that is one greater than necessary. The practical
upshot of this is just a bit of wasted memory (one long in the
height_to_maxindex array, an extra pre-allocated radix tree node per
cpu, and extra stack usage in a couple of functions), but it seems
worth getting right.

It's also worth noting that I never build with CONFIG_BASE_SMALL.
What I did to test this was duplicate the code in a small user-space
program and check the results of the calculations for max path and the
contents of the height_to_maxindex array.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radix-tree: use indirect bit

Rather than sign direct radix-tree pointers with a special bit, sign the
indirect one that hangs off the root. This means that, given a lookup_slot
operation, the invalid result will be differentiated from the valid
(previously, valid results could have the bit either set or clear).

This does not affect slot lookups which occur under lock -- they can never
return an invalid result. Is needed in future for lockless pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

radixtree: introduce radix_tree_next_hole()

Introduce radix_tree_next_hole(root, index, max_scan) to scan radix tree for
the first hole. It will be used in interleaved readahead.

The implementation is dumb and obviously correct. It can help debug(and
document) the possible smart one in future.

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: Remove slab destructors from kmem_cache_create().

Slab destructors were no longer supported after Christoph's
c59def9f222d44bb7e2f0a559f2906191a0862d7 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

[LIB]: export radix_tree_preload()

XFS filestreams functionality uses radix trees and the preload
functions. XFS can be built as a module and hence we need
radix_tree_preload() exported. radix_tree_preload_end() is a
static inline, so it doesn't need exporting.

Signed-Off-By: Dave Chinner <dgc@sgi.com>
Signed-Off-By: Tim Shimmin <tes@sgi.com>

Add suspend-related notifications for CPU hotplug

Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress. This
patch introduces such notifications and causes them to be used during
suspend and resume transitions. It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).

[oleg@tv-sign.ru: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

[PATCH] hotplug CPU: clean up hotcpu_notifier() use

There was lots of #ifdef noise in the kernel due to hotcpu_notifier(fn,
prio) not correctly marking 'fn' as used in the !HOTPLUG_CPU case, and thus
generating compiler warnings of unused symbols, hence forcing people to add
#ifdefs.

the compiler can skip truly unused functions just fine:

text data bss dec hex filename
1624412 728710 3674856 6027978 5bfaca vmlinux.before
1624412 728710 3674856 6027978 5bfaca vmlinux.after

[akpm@osdl.org: topology.c fix]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree: RCU lockless readside

Make radix tree lookups safe to be performed without locks. Readers are
protected against nodes being deleted by using RCU based freeing. Readers
are protected against new node insertion by using memory barriers to ensure
the node itself will be properly written before it is visible in the radix
tree.

Each radix tree node keeps a record of their height (above leaf nodes).
This height does not change after insertion -- when the radix tree is
extended, higher nodes are only inserted in the top. So a lookup can take
the pointer to what is *now* the root node, and traverse down it even if
the tree is concurrently extended and this node becomes a subtree of a new
root.

"Direct" pointers (tree height of 0, where root->rnode points directly to
the data item) are handled by using the low bit of the pointer to signal
whether rnode is a direct pointer or a pointer to a radix tree node.

When a reader wants to traverse the next branch, they will take a copy of
the pointer. This pointer will be either NULL (and the branch is empty) or
non-NULL (and will point to a valid node).

[akpm@osdl.org: cleanups]
[Lee.Schermerhorn@hp.com: bugfixes, comments, simplifications]
[clameter@sgi.com: build fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] slab: remove kmem_cache_t

Replace all uses of kmem_cache_t with struct kmem_cache.

The patch was generated using the following script:

#!/bin/sh
#
# Replace one string by another in all the kernel sources.
#

set -e

for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do
quilt add $file
sed -e "1,\$s/$1/$2/g" $file >/tmp/$$
mv /tmp/$$ $file
quilt refresh
done

The script was run like this

sh replace kmem_cache_t "struct kmem_cache"

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] gfp annotations: radix_tree_root

struct radix_tree_root has unused upper bits of ->gfp_mask reused for
tags bitmap. Annotated.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radixtree: normalize radix_tree_tag_get() return value

In radix_tree_tag_get(), return normalized value of 0/1, as indicated
by its comment.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] buglet in radix_tree_tag_set

The comment states: 'Setting a tag on a not-present item is a BUG.' Hence
if 'index' is larger than the maxindex; the item _cannot_ be presen; it
should also be a BUG.

Also, this allows the following statement (assume a fresh tree):

radix_tree_tag_set(root, 16, 1);

to fail silently, but when preceded by:

radix_tree_insert(root, 32, item);

it would BUG, because the height has been extended by the insert.

In neither case was 16 present.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree: small

Reduce radix tree node memory usage by about a factor of 4 for small files
(< 64K). There are pointer traversal and memory usage costs for large
files with dense pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree: direct data

The ability to have height 0 radix trees (a direct pointer to the data item
rather than going through a full node->slot) quietly disappeared with
old-2.6-bkcvs commit ffee171812d51652f9ba284302d9e5c5cc14bdfd. On 64-bit
machines this causes nearly 600 bytes to be used for every <= 4K file in
pagecache.

Re-introduce this feature, root tags stored in spare ->gfp_mask bits.

Simplify radix_tree_delete's complex tag clearing arrangement (which would
become even more complex) by just falling back to tag clearing functions
(the pagecache radix-tree never uses this path anyway, so the icache
savings will mean it's actually a speedup).

On my 4GB G5, this saves 8MB RAM per kernel kernel source+object tree in
pagecache.

Pagecache lookup, insertion, and removal speed for small files will also be
improved.

This makes RCU radix tree harder, but it's worth it.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree documentation cleanups

Documentation changes to help radix tree users avoid overrunning the tags
array. RADIX_TREE_TAGS moves to linux/radix-tree.h and is now known as
RADIX_TREE_MAX_TAGS (Nick Piggin's idea). Tag parameters are changed to
unsigned, and some comments are updated.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] Fix over-zealous tag clearing in radix_tree_delete

If a tag is set for a node being deleted from a radix_tree, then that
tag gets cleared from the parent of the node, even if it is set for some
siblings of the node begin deleted.

This patch changes the logic to include a test for any_tag_set similar
to the logic a little futher down. Care is taken to ensure that
'nr_cleared_tags' remains equals to the number of entries in the 'tags'
array which are set to '0' (which means that this tag is not set in the
tree below pathp->node, and should be cleared at pathp->node and
possibly above.

[ Nick says: "Linus FYI, I was able to modify the radix tree test
harness to catch the bug and can no longer trigger it after the fix.
Resulting code passes all other harness tests as well of course." ]

Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree: reduce tree height upon partial truncation

Shrink the height of a radix tree when it is partially truncated - we only do
shrinkage of full truncation at present.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix tree: early termination of tag clearing

Correctly determine the tags to be cleared in radix_tree_delete() so we
don't keep moving up the tree clearing tags that we don't need to. For
example, if a tag is simply not set in the deleted item, nor anywhere up
the tree, radix_tree_delete() would attempt to clear it up the entire
height of the tree.

Also, tag_set() was made conditional so as not to dirty too many cachelines
high up in the radix tree. Instead, put this logic into
radix_tree_tag_set().

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix tree: code consolidation

Introduce helper any_tag_set() rather than repeat the same code sequence 4
times.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] reiser4: add radix_tree_lookup_slot()

Reiser4 uses radix trees to solve a trouble reiser4_readdir has serving nfs
requests.

Unfortunately, radix tree api lacks an operation suitable for modifying
existing entry. This patch adds radix_tree_lookup_slot which returns pointer
to found item within the tree. That location can be then updated.

Both Nick and Christoph Lameter have patches which need this as well.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] gfp flags annotations - part 1

- added typedef unsigned int __nocast gfp_t;

- replaced __nocast uses for gfp flags with gfp_t - it gives exactly
the same warnings as far as sparse is concerned, doesn't change
generated code (from gcc point of view we replaced unsigned int with
typedef) and documents what's going on far better.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] lib/radix-tree: Fix "nocast type" warnings

Fix the sparse warning "implicit cast to nocast type"

Signed-off-by: Victor Fusco <victor@cetuc.puc-rio.br>
Signed-off-by: Domen Puncer <domen@coderock.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix_tag_get(): differentiate between no present node and tag unset cases

Simple patch to radix_tree_tag_get() to return different values for non
present node and tag unset.

The function is not used by any in-kernel callers (yet), but this
information is definitely useful.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] radix-tree: Remove unnecessary indirections and clean up code

- There is frequent use of indirections in the radix code. This patch
removes those indirections, makes the code more readable and allows
the compilers to generate better code.

- Removing indirections allows the removal of several casts.

- Removing indirections allows the reduction of the radix_tree_path
size from 3 to 2 words.

- Use pathp-> consistently.

- Remove unnecessary tmp variable in radix_tree_insert

- Separate the upper layer processing from the lowest layer in __lookup()
in order to make it easier to understand what is going on and allow
compilers to generate better code for the loop.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] mostly_read data section

Add a new section called ".data.read_mostly" for data items that are read
frequently and rarely written to like cpumaps etc.

If these maps are placed in the .data section then these frequenly read
items may end up in cachelines with data is is frequently updated. In that
case all processors in an SMP system must needlessly reload the cachelines
again and again containing elements of those frequently used variables.

The ability to share these cachelines will allow each cpu in an SMP system
to keep local copies of those shared cachelines thereby optimizing
performance.

Signed-off-by: Alok N Kataria <alokk@calsoftinc.com>
Signed-off-by: Shobhit Dayal <shobhit@calsoftinc.com>
Signed-off-by: Christoph Lameter <christoph@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!