When mempool_alloc() is allowed to sleep (GFP_NOIO allows
sleeping) it cannot fail.
So rpc_alloc_task() cannot fail, so rpc_new_task doesn't need
to test for failure.
Consequently rpc_new_task() cannot fail, so the callers
don't need to test.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

For xprtrdma, the RPC Call and Reply buffers are involved in real
I/O operations.

To start with, the DMA direction of the I/O for a Call is opposite
that of a Reply.

In the current arrangement, the Reply buffer address is on a
four-byte alignment just past the call buffer. Would be friendlier
on some platforms if that was at a DMA cache alignment instead.

Because the current arrangement allocates a single memory region
which contains both buffers, the RPC Reply buffer often contains a
page boundary in it when the Call buffer is large enough (which is
frequent).

It would be a little nicer for setting up DMA operations (and
possible registration of the Reply buffer) if the two buffers were
separated, well-aligned, and contained as few page boundaries as
possible.

Now, I could just pad out the single memory region used for the pair
of buffers. But frequently that would mean a lot of unused space to
ensure the Reply buffer did not have a page boundary.

Add a separate pointer to rpc_rqst that points right to the RPC
Reply buffer. This makes no difference to xprtsock, but it will help
xprtrdma in subsequent patches.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

xprtrdma needs to allocate the Call and Reply buffers separately.
TBH, the reliance on using a single buffer for the pair of XDR
buffers is transport implementation-specific.

Instead of passing just the rq_buffer into the buf_free method, pass
the task structure and let buf_free take care of freeing both
XDR buffers at once.

There's a micro-optimization here. In the common case, both
xprt_release and the transport's buf_free method were checking if
rq_buffer was NULL. Now the check is done only once per RPC.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

xprtrdma needs to allocate the Call and Reply buffers separately.
TBH, the reliance on using a single buffer for the pair of XDR
buffers is transport implementation-specific.

Transports that want to allocate separate Call and Reply buffers
will ignore the "size" argument anyway.  Don't bother passing it.

The buf_alloc method can't return two pointers. Instead, make the
method's return value an error code, and set the rq_buffer pointer
in the method itself.

This gives call_allocate an opportunity to terminate an RPC instead
of looping forever when a permanent problem occurs. If a request is
just bogus, or the transport is in a state where it can't allocate
resources for any request, there needs to be a way to kill the RPC
right there and not loop.

This immediately fixes a rare problem in the backchannel send path,
which loops if the server happens to send a CB request whose
call+reply size is larger than a page (which it shouldn't do yet).

One more issue: looks like xprt_inject_disconnect was incorrectly
placed in the failure path in call_allocate. It needs to be in the
success path, as it is for other call-sites.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Use the low latency transport workqueue to process the task that is
next in line on the xprt->sending queue.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

rpciod can easily get congested due to the long list of queued rpc_tasks.
Having the receive queue wait in turn for those tasks to complete can
therefore be a bottleneck.

Address the problem by separating the workqueues into:
- rpciod: manages rpc_tasks
- xprtiod: manages transport related work.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

This is needed in order to allow the NFSv4.1 backchannel and
BIND_CONN_TO_SESSION function to work.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Jan Stancek reported that I wrecked things for him by fixing things for
Vladimir :/

His report was due to an UNINTERRUPTIBLE wait getting -EINTR, which
should not be possible, however my previous patch made this possible by
unconditionally checking signal_pending().

We cannot use current->state as was done previously, because the
instruction after the store to that variable it can be changed.  We must
instead pass the initial state along and use that.

Fixes: 68985633 ("sched/wait: Fix signal handling in bit wait helpers")
Reported-by: NJan Stancek <jstancek@redhat.com>
Reported-by: NChris Mason <clm@fb.com>
Tested-by: NJan Stancek <jstancek@redhat.com>
Tested-by: NVladimir Murzin <vladimir.murzin@arm.com>
Tested-by: NChris Mason <clm@fb.com>
Reviewed-by: NPaul Turner <pjt@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: tglx@linutronix.de
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: hpa@zytor.com
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit 51360155 and adapts
fs/userfaultfd.c to use the old version of that function.

It didn't look robust to call __wake_up_common with "nr == 1" when we
absolutely require wakeall semantics, but we've full control of what we
insert in the two waitqueue heads of the blocked userfaults.  No
exclusive waitqueue risks to be inserted into those two waitqueue heads
so we can as well stick to "nr == 1" of the old code and we can rely
purely on the fact no waitqueue inserted in one of the two waitqueue
heads we must enforce as wakeall, has wait->flags WQ_FLAG_EXCLUSIVE set.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove unneeded NULL test.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@ expression x; @@
-if (x != NULL)
  \(kmem_cache_destroy\|mempool_destroy\|dma_pool_destroy\)(x);
// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

userfaultfd needs to wake all waitqueues (pass 0 as nr parameter), instead
of the current hardcoded 1 (that would wake just the first waitqueue in
the head list).
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Acked-by: NPavel Emelyanov <xemul@parallels.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fix build-warning introduced by commit: f0eede10 ("SUNRPC: use
jiffies_to_msecs for converting jiffies") which did not fixup
the format properly (my bad).
Signed-off-by: NNicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Use jiffies_to_msecs for converting jiffies as it handles all of the corner
cases reliably and also helps readability.
Signed-off-by: NNicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

We should be safe now, as long as we don't do GFP_IO or higher allocations
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Increase the concurrency level for rpciod threads to allow for allocations
etc that happen in the RPCSEC_GSS layer. Also note that the NFSv4 byte range
locks may now need to allocate memory from inside rpciod.

Add the WQ_HIGHPRI flag to improve latency guarantees while we're at it.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

It's always set to the same value as CONFIG_TRACEPOINTS, so we can just
use that instead.
Signed-off-by: NJeff Layton <jlayton@primarydata.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

It's always set to whatever CONFIG_SUNRPC_DEBUG is, so just use that.
Signed-off-by: NJeff Layton <jlayton@primarydata.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Now that nfs_release_page() doesn't block indefinitely, other deadlock
avoidance mechanisms aren't needed.
 - it doesn't hurt for kswapd to block occasionally.  If it doesn't
   want to block it would clear __GFP_WAIT.  The current_is_kswapd()
   was only added to avoid deadlocks and we have a new approach for
   that.
 - memory allocation in the SUNRPC layer can very rarely try to
   ->releasepage() a page it is trying to handle.  The deadlock
   is removed as nfs_release_page() doesn't block indefinitely.

So we don't need to set PF_FSTRANS for sunrpc network operations any
more.
Signed-off-by: NNeilBrown <neilb@suse.de>
Acked-by: NJeff Layton <jlayton@primarydata.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

It is currently not possible for various wait_on_bit functions
to implement a timeout.

While the "action" function that is called to do the waiting
could certainly use schedule_timeout(), there is no way to carry
forward the remaining timeout after a false wake-up.
As false-wakeups a clearly possible at least due to possible
hash collisions in bit_waitqueue(), this is a real problem.

The 'action' function is currently passed a pointer to the word
containing the bit being waited on.  No current action functions
use this pointer.  So changing it to something else will be a
little noisy but will have no immediate effect.

This patch changes the 'action' function to take a pointer to
the "struct wait_bit_key", which contains a pointer to the word
containing the bit so nothing is really lost.

It also adds a 'private' field to "struct wait_bit_key", which
is initialized to zero.

An action function can now implement a timeout with something
like

static int timed_out_waiter(struct wait_bit_key *key)
{
	unsigned long waited;
	if (key->private == 0) {
		key->private = jiffies;
		if (key->private == 0)
			key->private -= 1;
	}
	waited = jiffies - key->private;
	if (waited > 10 * HZ)
		return -EAGAIN;
	schedule_timeout(waited - 10 * HZ);
	return 0;
}

If any other need for context in a waiter were found it would be
easy to use ->private for some other purpose, or even extend
"struct wait_bit_key".

My particular need is to support timeouts in nfs_release_page()
to avoid deadlocks with loopback mounted NFS.

While wait_on_bit_timeout() would be a cleaner interface, it
will not meet my need.  I need the timeout to be sensitive to
the state of the connection with the server, which could change.
 So I need to use an 'action' interface.
Signed-off-by: NNeilBrown <neilb@suse.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steve French <sfrench@samba.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140707051604.28027.41257.stgit@notabene.brownSigned-off-by: NIngo Molnar <mingo@kernel.org>

rpc_malloc() allocates with GFP_NOWAIT without making any attempt at
reclaim so it easily fails when low on memory.  This ends up spamming the
kernel log:

SLAB: Unable to allocate memory on node 0 (gfp=0x4000)
  cache: kmalloc-8192, object size: 8192, order: 1
  node 0: slabs: 207/207, objs: 207/207, free: 0
rekonq: page allocation failure: order:1, mode:0x204000
CPU: 2 PID: 14321 Comm: rekonq Tainted: G           O  3.15.0-rc3-12.gfc9498b-desktop+ #6
Hardware name: System manufacturer System Product Name/M4A785TD-V EVO, BIOS 2105    07/23/2010
 0000000000000000 ffff880010ff17d0 ffffffff815e693c 0000000000204000
 ffff880010ff1858 ffffffff81137bd2 0000000000000000 0000001000000000
 ffff88011ffebc38 0000000000000001 0000000000204000 ffff88011ffea000
Call Trace:
 [<ffffffff815e693c>] dump_stack+0x4d/0x6f
 [<ffffffff81137bd2>] warn_alloc_failed+0xd2/0x140
 [<ffffffff8113be19>] __alloc_pages_nodemask+0x7e9/0xa30
 [<ffffffff811824a8>] kmem_getpages+0x58/0x140
 [<ffffffff81183de6>] fallback_alloc+0x1d6/0x210
 [<ffffffff81183be3>] ____cache_alloc_node+0x123/0x150
 [<ffffffff81185953>] __kmalloc+0x203/0x490
 [<ffffffffa06b0ee2>] rpc_malloc+0x32/0xa0 [sunrpc]
 [<ffffffffa06a6999>] call_allocate+0xb9/0x170 [sunrpc]
 [<ffffffffa06b19d8>] __rpc_execute+0x88/0x460 [sunrpc]
 [<ffffffffa06b2da9>] rpc_execute+0x59/0xc0 [sunrpc]
 [<ffffffffa06a932b>] rpc_run_task+0x6b/0x90 [sunrpc]
 [<ffffffffa077b5c1>] nfs4_call_sync_sequence+0x51/0x80 [nfsv4]
 [<ffffffffa077d45d>] _nfs4_do_setattr+0x1ed/0x280 [nfsv4]
 [<ffffffffa0782a72>] nfs4_do_setattr+0x72/0x180 [nfsv4]
 [<ffffffffa078334c>] nfs4_proc_setattr+0xbc/0x140 [nfsv4]
 [<ffffffffa074a7e8>] nfs_setattr+0xd8/0x240 [nfs]
 [<ffffffff811baa71>] notify_change+0x231/0x380
 [<ffffffff8119cf5c>] chmod_common+0xfc/0x120
 [<ffffffff8119df80>] SyS_chmod+0x40/0x90
 [<ffffffff815f4cfd>] system_call_fastpath+0x1a/0x1f
...

If the allocation fails, simply return NULL and avoid spamming the kernel
log.
Reported-by: NMarc Dietrich <marvin24@gmx.de>
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

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

The RPC_TASK_RUNNING flag will always have been set in rpc_make_runnable()
once we get past the test for out_of_line_wait_on_bit() returning
ERESTARTSYS.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

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

If the rpc_task is asynchronous, it could theoretically finish executing
on the workqueue it was assigned by rpc_make_runnable() before we get
round to testing RPC_IS_ASYNC() in rpc_execute.

In practice, however, all the existing callers hold a reference to the
rpc_task, so this can't happen today...
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The lockless RPC_IS_QUEUED() test in __rpc_execute means that we need to
be careful about ordering the calls to rpc_test_and_set_running(task) and
rpc_clear_queued(task). If we get the order wrong, then we may end up
testing the RPC_TASK_RUNNING flag after __rpc_execute() has looped
and changed the state of the rpc_task.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org

NFS calls the freezable helpers with locks held, which is unsafe
and will cause lockdep warnings when 6aa97070 "lockdep: check
that no locks held at freeze time" is reapplied (it was reverted
in dbf520a9).  NFS shouldn't be doing this, but it has
long-running syscalls that must hold a lock but also shouldn't
block suspend.  Until NFS freeze handling is rewritten to use a
signal to exit out of the critical section, add new *_unsafe
versions of the helpers that will not run the lockdep test when
6aa97070 is reapplied, and call them from NFS.

In practice the likley result of holding the lock while freezing
is that a second task blocked on the lock will never freeze,
aborting suspend, but it is possible to manufacture a case using
the cgroup freezer, the lock, and the suspend freezer to create
a deadlock.  Silencing the lockdep warning here will allow
problems to be found in other drivers that may have a more
serious deadlock risk, and prevent new problems from being added.
Signed-off-by: NColin Cross <ccross@android.com>
Acked-by: NPavel Machek <pavel@ucw.cz>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We need to be careful when testing task->tk_waitqueue in
rpc_wake_up_task_queue_locked, because it can be changed while we
are holding the queue->lock.
By adding appropriate memory barriers, we can ensure that it is safe to
test task->tk_waitqueue for equality if the RPC_TASK_QUEUED bit is set.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org

This fixes a livelock in the xprt->sending queue where we end up never
making progress on lower priority tasks because sleep_on_priority()
keeps adding new tasks with the same owner to the head of the queue,
and priority bumps mean that we keep resetting the queue->owner to
whatever task is at the head of the queue.

Regression introduced by commit c05eecf6
(SUNRPC: Don't allow low priority tasks to pre-empt higher priority ones).
Reported-by: NAndy Adamson <andros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

If the rpc_task exits while holding the socket write lock before it has
allocated an rpc slot, then the usual mechanism for releasing the write
lock in xprt_release() is defeated.

The problem occurs if the call to xprt_lock_write() initially fails, so
that the rpc_task is put on the xprt->sending wait queue. If the task
exits after being assigned the lock by __xprt_lock_write_func, but
before it has retried the call to xprt_lock_and_alloc_slot(), then
it calls xprt_release() while holding the write lock, but will
immediately exit due to the test for task->tk_rqstp != NULL.
Reported-by: NChris Perl <chris.perl@gmail.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org [>= 3.1]

This patch ensures that we free the rpc_task after the cleanup callbacks
are done in order to avoid a deadlock problem that can be triggered if
the callback needs to wait for another workqueue item to complete.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: Weston Andros Adamson <dros@netapp.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Bruce Fields <bfields@fieldses.org>
Cc: stable@vger.kernel.org

Currently, the priority queues attempt to be 'fair' to lower priority
tasks by scheduling them after a certain number of higher priority tasks
have run. The problem is that both the transport send queue and
the NFSv4.1 session slot queue have strong ordering requirements.

This patch therefore removes the fairness code in favour of strong
ordering of task priorities.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We want to preserve the rpc_task priority for things like writebacks,
that may have differing levels of urgency.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Replace BUG_ON() with WARN_ON_ONCE().
Signed-off-by: NWeston Andros Adamson <dros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Replace two BUG_ON() calls with WARN_ON_ONCE() and early returns.
Signed-off-by: NWeston Andros Adamson <dros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Replace BUG_ON() with WARN_ON_ONCE().
Signed-off-by: NWeston Andros Adamson <dros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Replace BUG_ON() with WARN_ON_ONCE() and clean up after inactive task.
Signed-off-by: NWeston Andros Adamson <dros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We shouldn't need more than 1 worker thread per cpu, since rpciod
is designed to run without sleeping in most cases.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Implement the new swapfile a_ops for NFS and hook up ->direct_IO.  This
will set the NFS socket to SOCK_MEMALLOC and run socket reconnect under
PF_MEMALLOC as well as reset SOCK_MEMALLOC before engaging the protocol
->connect() method.

PF_MEMALLOC should allow the allocation of struct socket and related
objects and the early (re)setting of SOCK_MEMALLOC should allow us to
receive the packets required for the TCP connection buildup.

[jlayton@redhat.com: Restore PF_MEMALLOC task flags in all cases]
[dfeng@redhat.com: Fix handling of multiple swap files]
[a.p.zijlstra@chello.nl: Original patch]
Signed-off-by: NMel Gorman <mgorman@suse.de>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We've had some reports of a deadlock where rpciod ends up with a stack
trace like this:

    PID: 2507   TASK: ffff88103691ab40  CPU: 14  COMMAND: "rpciod/14"
     #0 [ffff8810343bf2f0] schedule at ffffffff814dabd9
     #1 [ffff8810343bf3b8] nfs_wait_bit_killable at ffffffffa038fc04 [nfs]
     #2 [ffff8810343bf3c8] __wait_on_bit at ffffffff814dbc2f
     #3 [ffff8810343bf418] out_of_line_wait_on_bit at ffffffff814dbcd8
     #4 [ffff8810343bf488] nfs_commit_inode at ffffffffa039e0c1 [nfs]
     #5 [ffff8810343bf4f8] nfs_release_page at ffffffffa038bef6 [nfs]
     #6 [ffff8810343bf528] try_to_release_page at ffffffff8110c670
     #7 [ffff8810343bf538] shrink_page_list.clone.0 at ffffffff81126271
     #8 [ffff8810343bf668] shrink_inactive_list at ffffffff81126638
     #9 [ffff8810343bf818] shrink_zone at ffffffff8112788f
    #10 [ffff8810343bf8c8] do_try_to_free_pages at ffffffff81127b1e
    #11 [ffff8810343bf958] try_to_free_pages at ffffffff8112812f
    #12 [ffff8810343bfa08] __alloc_pages_nodemask at ffffffff8111fdad
    #13 [ffff8810343bfb28] kmem_getpages at ffffffff81159942
    #14 [ffff8810343bfb58] fallback_alloc at ffffffff8115a55a
    #15 [ffff8810343bfbd8] ____cache_alloc_node at ffffffff8115a2d9
    #16 [ffff8810343bfc38] kmem_cache_alloc at ffffffff8115b09b
    #17 [ffff8810343bfc78] sk_prot_alloc at ffffffff81411808
    #18 [ffff8810343bfcb8] sk_alloc at ffffffff8141197c
    #19 [ffff8810343bfce8] inet_create at ffffffff81483ba6
    #20 [ffff8810343bfd38] __sock_create at ffffffff8140b4a7
    #21 [ffff8810343bfd98] xs_create_sock at ffffffffa01f649b [sunrpc]
    #22 [ffff8810343bfdd8] xs_tcp_setup_socket at ffffffffa01f6965 [sunrpc]
    #23 [ffff8810343bfe38] worker_thread at ffffffff810887d0
    #24 [ffff8810343bfee8] kthread at ffffffff8108dd96
    #25 [ffff8810343bff48] kernel_thread at ffffffff8100c1ca

rpciod is trying to allocate memory for a new socket to talk to the
server. The VM ends up calling ->releasepage to get more memory, and it
tries to do a blocking commit. That commit can't succeed however without
a connected socket, so we deadlock.

Fix this by setting PF_FSTRANS on the workqueue task prior to doing the
socket allocation, and having nfs_release_page check for that flag when
deciding whether to do a commit call. Also, set PF_FSTRANS
unconditionally in rpc_async_schedule since that function can also do
allocations sometimes.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org