I ran into a curious issue when a lock is being canceled. The
cancellation results in a lock request to the vfs layer instead of an
unlock request. This is particularly insidious when the process that
owns the lock is exiting. In that case, sometimes the erroneous lock is
applied AFTER the process has entered zombie state, preventing the lock
from ever being released. Eventually other processes block on the lock
causing a slow degredation of the system. In the 2.6.16 kernel this was
investigated on, the problem is compounded by the fact that the cl_sem
is held while blocking on the vfs lock, which results in most processes
accessing the nfs file system in question hanging.

In more detail, here is how the situation occurs:

first _nfs4_do_setlk():

static int _nfs4_do_setlk(struct nfs4_state *state, int cmd, struct file_lock *fl, int reclaim)
...
        ret = nfs4_wait_for_completion_rpc_task(task);
        if (ret == 0) {
...
        } else
                data->cancelled = 1;

then nfs4_lock_release():

static void nfs4_lock_release(void *calldata)
...
        if (data->cancelled != 0) {
                struct rpc_task *task;
                task = nfs4_do_unlck(&data->fl, data->ctx, data->lsp,
                                data->arg.lock_seqid);

The problem is the same file_lock that was passed in to _nfs4_do_setlk()
gets passed to nfs4_do_unlck() from nfs4_lock_release(). So the type is
still F_RDLCK or FWRLCK, not F_UNLCK. At some point, when cancelling the
lock, the type needs to be changed to F_UNLCK. It seemed easiest to do
that in nfs4_do_unlck(), but it could be done in nfs4_lock_release().
The concern I had with doing it there was if something still needed the
original file_lock, though it turns out the original file_lock still
needs to be modified by nfs4_do_unlck() because nfs4_do_unlck() uses the
original file_lock to pass to the vfs layer, and a copy of the original
file_lock for the RPC request.

It seems like the simplest solution is to force all situations where
nfs4_do_unlck() is being used to result in an unlock, so with that in
mind, I made the following change:
Signed-off-by: NFrank Filz <ffilzlnx@us.ibm.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We really don't need to grab both the state->so_owner and the
inode->i_lock.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Rely on nfs4_try_open_cached() when appropriate.

Also fix an RCU violation in _nfs4_do_open_reclaim()
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

If we already have a stateid with the correct open mode for a given file,
then we can reuse that stateid instead of re-issuing an OPEN call without
violating the close-to-open caching semantics.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We should not be calling open() on an inode that has a delegation unless
we're doing a reclaim.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Use a flag instead of the 'data->rpc_status = -ENOMEM hack.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Don't clobber the delegation info...
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

This ensures that nfs4_open_release() and nfs4_open_confirm_release()
can now handle an eventual delegation that was returned with out open.
As such, it fixes a delegation "leak" when the user breaks out of an open
call.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Currently we do not check for the FMODE_EXEC flag as we should. For that
particular case, we need to perform an ACCESS call to the server in order
to check that the file is executable.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Currently we just use a 32-bit counter.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

They differ only slightly in the arguments they take. Why have they not
been merged?
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The Linux NFS4 client simply skips over the bitmask in an O_EXCL open
call and so it doesn't bother to reset any fields that may be holding
the verifier. This patch has us save the first two words of the bitmask
(which is all the current client has #defines for). The client then
later checks this bitmask and turns on the appropriate flags in the
sattr->ia_verify field for the following SETATTR call.

This patch only currently checks to see if the server used the atime
and mtime slots for the verifier (which is what the Linux server uses
for this). I'm not sure of what other fields the server could
reasonably use, but adding checks for others should be trivial.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Use rpc_run_task() instead of doing it ourselves.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

nfs4_do_close() does not currently have any way to ensure that the user
won't attempt to unmount the partition while the asynchronous RPC call
is completing. This again may cause Oopses in nfs_update_inode().

Add a vfsmount argument to nfs4_close_state to ensure that the partition
remains mounted while we're closing the file.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

A number of race conditions may currently ensue if the user presses ^C
and then unmounts the partition while an asynchronous open() is in
progress.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 - fs/nfs/dir.c:610:8: warning: symbol 'nfs_llseek_dir' was not declared.
   Should it be static?
 - fs/nfs/dir.c:636:5: warning: symbol 'nfs_fsync_dir' was not declared.
   Should it be static?
 - fs/nfs/write.c:925:19: warning: symbol 'req' shadows an earlier one
 - fs/nfs/write.c:61:6: warning: symbol 'nfs_commit_rcu_free' was not
   declared. Should it be static?
 - fs/nfs/nfs4proc.c:793:5: warning: symbol 'nfs4_recover_expired_lease'
   was not declared. Should it be static?
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The file_lock argument to ->lock is used to return the conflicting lock
when found.  There's no reason for the filesystem to return any private
information with this conflicting lock, but nfsv4 is.

Fix nfsv4 client, and modify locks.c to stop calling fl_release_private
for it in this case.
Signed-off-by: N"J. Bruce Fields" <bfields@citi.umich.edu>
Cc: "Trond Myklebust" <Trond.Myklebust@netapp.com>"

The ACL that the server sets may not be exactly the one we set--for
example, it may silently turn off bits that it does not support.  So we
should remove any cached ACL so that any subsequent request for the ACL
will go to the server.
Signed-off-by: N"J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Many struct inode_operations in the kernel can be "const".  Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data.  In addition it'll catch accidental writes at compile time to
these shared resources.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Attempt to detect deadlocks due to caller holding locks on clp->cl_sem
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We might not even have any open files at this point...
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

It makes no sense to maintain 2 parallel systems for reading in pages.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Start long arduous project...  What the hell is

	struct dentry = {};

all about?
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Run this:

	#!/bin/sh
	for f in $(grep -Erl "\([^\)]*\) *k[cmz]alloc" *) ; do
	  echo "De-casting $f..."
	  perl -pi -e "s/ ?= ?\([^\)]*\) *(k[cmz]alloc) *\(/ = \1\(/" $f
	done

And then go through and reinstate those cases where code is casting pointers
to non-pointers.

And then drop a few hunks which conflicted with outstanding work.

Cc: Russell King <rmk@arm.linux.org.uk>, Ian Molton <spyro@f2s.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Greg KH <greg@kroah.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Karsten Keil <kkeil@suse.de>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Steven French <sfrench@us.ibm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Cc: Jaroslav Kysela <perex@suse.cz>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Maintaining two parallel ways of doing synchronous writes is rather
pointless. This patch gets rid of the legacy nfs_writepage_sync(), and
replaces it with the faster asynchronous writes.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Remove use of the Big Kernel Lock around calls to rpc_call_sync.
Signed-off-by: NFrank Filz <ffilz@us.ibm.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Acked-by: NTrond Myklebust <trond.myklebust@fys.uio.no>
Acked-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

on-the-wire data is big-endian

[in large part pulled from Alexey's patch]
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Acked-by: NTrond Myklebust <trond.myklebust@fys.uio.no>
Acked-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Coverity spotted a superfluous error check in nfs4_open_revalidate().  Remove
it.

Coverity: #cid 847

Test plan:
Code inspection; another pass through Coverity.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Change the initial retry delay from 1s to 0.1s (and then back off
exponentially).
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Retry a few times before we give up: the error is usually due to ordering
issues with asynchronous RPC calls.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>