MFC: r323689
Fix bogus FREAD with NFSV4OPEN_ACCESSREAD. No functional change.

The code in nfscl_doflayoutio() bogusly used FREAD instead of
NFSV4OPEN_ACCESSREAD. Since both happen to be defined as "1", this
worked and the patch doesn't result in a functional change.
Found by inspection during development of Flex File Layout support.

MFC: r321314
r320062 introduced a bug when doing NFSv4.1 mounts against some non-FreeBSD servers.

r320062 used nm_rsize, nm_wsize to set the maximum request/response sizes for
the NFSv4.1 session. If rsize,wsize are not specified as options, the
value of nm_rsize, nm_wsize is 0 at session creation, resulting in
values for request/response that are too small.
This patch fixes the problem. A workaround is to specify rsize=N,wsize=N
mount options explicitly, so they are set before session creation.
This bug only affects NFSv4.1 mounts against some non-FreeBSD servers.

MFC: r320345
Add support to the NFSv4.1/pNFS client for commits through the DS.

A NFSv4.1/pNFS server using File Layout can specify that Commit operations
are to be done against the DS instead of MDS. Since no extant pNFS
server did this, the code was untested and "#ifdef notyet".
The FreeBSD pNFS server I am developing does specify that Commits be done
through the DS, so the code has been enabled/tested.
This patch should only affect the case of a pNFS server that specfies
Commits through the DS.

Relnotes: yes

MFC: r320062, r320070, r320126
This is a partial merge of only the NFS changes and not the maxbcachebuf
tunable.

The NFS client changes make the code handle different I/O sizes more
correctly. However, with the limit at 64K, they are not actually
necessary.
This MFC is mainly being done so that subsequent MFCs to the NFS
code will merge easily.

MFC: r317576
Modify the NFSv4.1/pNFS client to ask for a maximum length of layout.

The code specified the length of a layout as INT64_MAX instead of
UINT64_MAX. This could result in getting a layout for less than the
full file for extremely large files. Although having little practical
effect, this patch corrects this in the code.
Detected during recent testing of the pNFS server.

MFC: r317345
Make the NFSv4 client to use a write open for reading if allowed by the server.

An NFSv4 server has the option of allowing a Read to be done using a Write
Open. If this is not allowed, the server will return NFSERR_OPENMODE.
This patch attempts the read with a write open and then disables this
if the server replies NFSERR_OPENMODE.
This change will avoid some uses of the special stateids. This will be
useful for pNFS/DS Reads, since they cannot use special stateids.
It will also be useful for any NFSv4 server that does not support reading
via the special stateids. It has been tested against both types of NFSv4 server.

MFC: r317296
Fix some krpc leaks for the NFSv4.1/pNFS client.

The NFSv4.1/pNFS client wasn't doing a newnfs_disconnect() call for the
connection to the Data Server (DS) under some circumstances. The main
effect of this was a leak of malloc'd structures in the krpc. This patch
adds the newnfs_disconnect() calls to fix this.
Detected during recent testing against the pNFS server under development.

MFC: r317275, r317344
Don't create a backchannel for a DS connection.

An NFSv4.1 client connection to a Data Server (DS) should not have a
backchannel. This patch fixes the NFSv4.1/pNFS client to not do a backchannel
for this case.
Found during recent testing with the pNFS server under development.

MFC: r316792
Add an NFSv4.1 mount option for "use one openowner".

Some NFSv4.1 servers such as AmazonEFS can only support a small fixed number
of open_owner4s. This patch adds a mount option called "oneopenown" that
can be used for NFSv4.1 mounts to make the client do all Opens with the
same open_owner4 string. This option can only be used with NFSv4.1 and
may not work correctly when Delegations are is use.

Differential Revision: https://reviews.freebsd.org/D8988

MFC: r316655
Fix parsing failure for NFSv4 Setattr operation for failed case.

If an operation that preceeds a Setattr in an NFSv4 compound fails,
there is no bitmap of attributes to parse. Without this patch, the
parsing would fail and return EBADRPC instead of the correct failure
error. This could break recovery from a server crash/reboot.

MFC: r310491
Fix NFSv4.1 client recovery from NFS4ERR_BAD_SESSION errors.

For most NFSv4.1 servers, a NFS4ERR_BAD_SESSION error is a rare failure
that indicates that the server has lost session/open/lock state.
However, recent testing by cperciva@ against the AmazonEFS server found
several problems with client recovery from this due to it generating this
failure frequently.
Briefly, the problems fixed are:
- If all session slots were in use at the time of the failure, some processes
would continue to loop waiting for a slot on the old session forever.
- If an RPC that doesn't use open/lock state failed with NFS4ERR_BAD_SESSION,
it would fail the RPC/syscall instead of initiating recovery and then
looping to retry the RPC.
- If a successful reply to an RPC for an old session wasn't processed
until after a new session was created for a NFS4ERR_BAD_SESSION error,
it would erroneously update the new session and corrupt it.
- The use of the first element of the session list in the nfs mount
structure (which is always the current metadata session) was slightly
racey. With changes for the above problems it became more racey, so all
uses of this head pointer was wrapped with a NFSLOCKMNT()/NFSUNLOCKMNT().
- Although the kernel malloc() usually allocates more bytes than requested
and, as such, this wouldn't have caused problems, the allocation of a
session structure was 1 byte smaller than it should have been.
(Null termination byte for the string not included in byte count.)

There are probably still problems with a pNFS data server that fails
with NFS4ERR_BAD_SESSION, but I have no server that does this to test
against (the AmazonEFS server doesn't do pNFS), so I can't fix these yet.

Although this patch is fairly large, it should only affect the handling
of NFS4ERR_BAD_SESSION error replies from an NFSv4.1 server.
Thanks go to cperciva@ for the extension testing he did to help isolate/fix
these problems.

MFC: r297837
Bruce Evans reported that there was a performance regression between
the old and new NFS clients. He did a good job of isolating the problem
which was caused by the new NFS client not setting the post write mtime
correctly. The new NFS client code was cloned from the old client, but
was incorrect, because the mtime in the nfs vnode's cache wasn't yet
updated. This patch fixes this problem. The patch also adds missing mutex
locking.

MFC: r291117
Revert r283330 since it broke directory caching in the client.
At this time I cannot see a way to fix directory caching when it
has partial blocks in the buffer cache, due to the fact that the
syscall's uio_offset won't stay the same as the lblkno * NFS_DIRBLKSIZ
offset.

MFC: r285066
Alex Burlyga reported a POLA violation for the new NFS client as
compared to the old NFS client via email to the freebsd-fs@ mailing list.
For the new client, when multiple clients attempted to create a symbolic
link concurrently, more that one client would report success instead of
EEXIST. This was caused by code in the new client that mapped EEXIST to
OK assuming it was caused by a retried RPC request.
Since the old client did not do this, the patch defaults to the old
behaviour and permits the new behaviour to be enabled via a sysctl.

MFC: r283330
The NFS client generated directory block(s) with d_fileno == 0
so that it would not return less data than requested.
Since returning less directory data than requested is not a problem
for FreeBSD and even UFS no longer returns directory structures
with d_fileno == 0, this patch stops the client from doing this.
Although entries with d_fileno == 0 should not be a problem,
the man pages no longer document that these entries should be
ignored, so there was a concern that these entries might be an
issue in the future.

MFC r281756:
nfsrpc_createv4: fix double free.

Reported by: Oliver Pinter, clang static checker
Obtained from: HardenedBSD (63cac77c42c0c3fc67da62f97d5ab651d52ae707)
Reviewed by: rmacklem

MFC: r264705, r264749
Modify the NFSv4 client create/mkdir RPC so that it acquires
post-create/mkdir directory attributes. This allows the RPC to
name cache the newly created directory and reduces the lookup RPC
count for applications creating a lot of directories.

MFC: r264681
Modify the NFSv4 client open/create RPC so that it acquires
post-open/create directory attributes. This allows the RPC to
name cache the newly created file and reduces the lookup RPC
count by about 10% for software builds.

MFC: r264672
Modify the Lookup RPC for NFSv4 so that it acquires directory
attributes. This allows the client to cache directory names
when they are looked up, reducing the Lookup RPC count by
about 40% for software builds.

MFC: r285066
Alex Burlyga reported a POLA violation for the new NFS client as
compared to the old NFS client via email to the freebsd-fs@ mailing list.
For the new client, when multiple clients attempted to create a symbolic
link concurrently, more that one client would report success instead of
EEXIST. This was caused by code in the new client that mapped EEXIST to
OK assuming it was caused by a retried RPC request.
Since the old client did not do this, the patch defaults to the old
behaviour and permits the new behaviour to be enabled via a sysctl.

MFC: r283330
The NFS client generated directory block(s) with d_fileno == 0
so that it would not return less data than requested.
Since returning less directory data than requested is not a problem
for FreeBSD and even UFS no longer returns directory structures
with d_fileno == 0, this patch stops the client from doing this.
Although entries with d_fileno == 0 should not be a problem,
the man pages no longer document that these entries should be
ignored, so there was a concern that these entries might be an
issue in the future.

MFC r281756:
nfsrpc_createv4: fix double free.

Reported by: Oliver Pinter, clang static checker
Obtained from: HardenedBSD (63cac77c42c0c3fc67da62f97d5ab651d52ae707)
Reviewed by: rmacklem

MFC: r264705, r264749
Modify the NFSv4 client create/mkdir RPC so that it acquires
post-create/mkdir directory attributes. This allows the RPC to
name cache the newly created directory and reduces the lookup RPC
count for applications creating a lot of directories.

MFC: r264681
Modify the NFSv4 client open/create RPC so that it acquires
post-open/create directory attributes. This allows the RPC to
name cache the newly created file and reduces the lookup RPC
count by about 10% for software builds.

MFC: r264672
Modify the Lookup RPC for NFSv4 so that it acquires directory
attributes. This allows the client to cache directory names
when they are looked up, reducing the Lookup RPC count by
about 40% for software builds.