MFC: r334252
Fix the sleep event for layout recall.

The sleep for I/O completion during an NFSv4.1 pNFS layout recall used
the wrong event value and could result in the "[nfscl]" thread hung
for the mount.
This patch fixes the event to be the correct.
This bug will only affect NFSv4.1 pnfs mounts and only when the server
does a layout recall callback, so it won't affect many. Without the patch,
a mount without the "pnfs" option will avoid the problem.
Found during testing of the pNFS server.

MFC: r324074
Fix a memory leak that occurred in the pNFS client.

When a "pnfs" NFSv4.1 mount was unmounted, it didn't free up the layouts
and deviceinfo structures. This leak only affects "pnfs" mounts and only
when the mount is umounted.
Found while testing the pNFS Flexible File layout client code.

MFC: r320208
Ensure that the credentials field of the NFSv4 client open structure is
initialized.

bdrewery@ has reported panics "newnfs_copycred: negative nfsc_ngroups".
The only way I can see that this occurs is that the credentials field of
the open structure gets used before being filled in.
I am not sure quite how this happens, but for the file create case, the
code is serialized via the vnode lock on the directory. If, somehow, a
link to the same file gets created just after file creation, this might
occur.

This patch ensures that the credentials field is initialized to a reasonable
set of credentials before the structure is linked into any list, so I
this should ensure it is initialized before use.
I am committing the patch now, since bdrewery@ notes that the panics
are intermittent and it may be months before he knows if the patch fixes
his problem.

MFC: r317465
Fix handling of a NFSv4.1 callback reply from the session cache.

The nfsv4_seqsession() call returns NFSERR_REPLYFROMCACHE when it has a
reply in the session, due to a requestor retry. The code erroneously
assumed a return of 0 for this case. This patch fixes this and adds
a KASSERT(). This would be an extremely rare occurrence. It was found
during code inspection during the pNFS server development.

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: r317305
Fix the NFSv4.1/pNFS client return layout on close.

The "return layout on close" case in the pNFS client was badly broken.
Fortunately, extant pNFS servers that I have tested against do not
do this. This patch fixes it. It also changes the way the layout stateid.seqid
is set for LayoutReturn. I think this change is correct w.r.t. the RFC,
but I am not 100% sure.
This was found during recent testing of the pNFS server under development.

MFC: r316829
Remove unused "cred" argument to ncl_flush().

The "cred" argument of ncl_flush() is unused and it was confusing to have
the code passing in NULL for this argument in some cases. This patch deletes
this argument.
There is no semantic change because of this patch.

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: r316719
Don't throw away Open state when a NFSv4.1 client recovery fails.

If the ExchangeID/CreateSession operations done by an NFSv4.1 client
after the server crashes/reboots fails, it is possible that some process/thread
is waiting for an open_owner lock. If the client state is free'd, this
can cause a crash.
This would not normally happen, but has been observed on a mount of the
AmazonEFS service.

MFC: r316717
During a server crash recovery, fix the NFSv4.1 client for a NFSERR_BADSESSION
during recovery.

If the NFSv4.1 client gets a NFSv4.1 NFSERR_BADSESSION reply to an Open/Lock
operation while recovering from the server crash/reboot, allow the opens
to be retained for a subsequent recovery attempt. Since NFSv4.1 servers
should only reply NFSERR_BADSESSION after a crash/reboot that has lost
state, this case should almost never happen.
However, for the AmazonEFS file service, this has been observed when
the client does a fresh TCP connection for RPCs.

MFC: r316669
Avoid starvation of the server crash recovery thread for the NFSv4 client.

This patch gives a requestor of the exclusive lock on the client state
in the NFSv4 client priority over shared lock requestors. This avoids
the server crash recovery thread being starved out by other threads doing
RPCs.

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.

Revert r306659 since the userland changes won't merge and this would
break the build.

MFC: r304026
Update the nfsstats structure to include the changes needed by
the patch in D1626 plus changes so that it includes counts for
NFSv4.1 (and the draft of NFSv4.2).
Also, make all the counts uint64_t and add a vers field at the
beginning, so that future revisions can easily be implemented.
There is code in place to handle the old vesion of the nfsstats
structure for backwards binary compatibility.

Subsequent commits will update nfsstat(8) to use the new fields.

MFC: r268115
Merge the NFSv4.1 server code in projects/nfsv4.1-server over
into head. The code is not believed to have any effect
on the semantics of non-NFSv4.1 server behaviour.
It is a rather large merge, but I am hoping that there will
not be any regressions for the NFS server.

MFC: r268008
There might be a potential race condition for the NFSv4 client
when a newly created file has another open done on it that
update the open mode. This patch moves the code that updates
the open mode up into the block where the mutex is held to
ensure this cannot happen. No bug caused by this potential
race has been observed, but this fix is a safety belt to ensure
it cannot happen.

MFC: r259801
The NFSv4 client was passing both the p and cred arguments to
nfsv4_fillattr() as NULLs for the Getattr callback. This caused
nfsv4_fillattr() to not fill in the Change attribute for the reply.
I believe this was a violation of the RFC, but had little effect on
server behaviour. This patch passes a non-NULL p argument to fix this.

MFC: r259771
The NFSv4.1 client didn't return NFSv4.1 specific error codes
for the Getattr and Recall callbacks. This patch fixes it.
Since the NFSv4.1 specific error codes would only happen for
abnormal circumstances, this patch has little effect, in practice.

MFC: r268115
Merge the NFSv4.1 server code in projects/nfsv4.1-server over
into head. The code is not believed to have any effect
on the semantics of non-NFSv4.1 server behaviour.
It is a rather large merge, but I am hoping that there will
not be any regressions for the NFS server.

MFC: r268008
There might be a potential race condition for the NFSv4 client
when a newly created file has another open done on it that
update the open mode. This patch moves the code that updates
the open mode up into the block where the mutex is held to
ensure this cannot happen. No bug caused by this potential
race has been observed, but this fix is a safety belt to ensure
it cannot happen.

MFC: r259801
The NFSv4 client was passing both the p and cred arguments to
nfsv4_fillattr() as NULLs for the Getattr callback. This caused
nfsv4_fillattr() to not fill in the Change attribute for the reply.
I believe this was a violation of the RFC, but had little effect on
server behaviour. This patch passes a non-NULL p argument to fix this.

MFC: r259771
The NFSv4.1 client didn't return NFSv4.1 specific error codes
for the Getattr and Recall callbacks. This patch fixes it.
Since the NFSv4.1 specific error codes would only happen for
abnormal circumstances, this patch has little effect, in practice.