NFS: Always wait for I/O completion before unlock
authorBenjamin Coddington <bcodding@redhat.com>
Tue, 11 Apr 2017 16:50:12 +0000 (12:50 -0400)
committerTrond Myklebust <trond.myklebust@primarydata.com>
Fri, 21 Apr 2017 14:45:01 +0000 (10:45 -0400)
commitf30cb757f680f965ba8a2e53cb3588052a01aeb5
tree071e925905e0931b326f5474619adb0aa645d07b
parentb1ece737f44f91dca8f4829cf0b442e752e406db
NFS: Always wait for I/O completion before unlock

NFS attempts to wait for read and write completion before unlocking in
order to ensure that the data returned was protected by the lock.  When
this waiting is interrupted by a signal, the unlock may be skipped, and
messages similar to the following are seen in the kernel ring buffer:

[20.167876] Leaked locks on dev=0x0:0x2b ino=0x8dd4c3:
[20.168286] POSIX: fl_owner=ffff880078b06940 fl_flags=0x1 fl_type=0x0 fl_pid=20183
[20.168727] POSIX: fl_owner=ffff880078b06680 fl_flags=0x1 fl_type=0x0 fl_pid=20185

For NFSv3, the missing unlock will cause the server to refuse conflicting
locks indefinitely.  For NFSv4, the leftover lock will be removed by the
server after the lease timeout.

This patch fixes this issue by skipping the usual wait in
nfs_iocounter_wait if the FL_CLOSE flag is set when signaled.  Instead, the
wait happens in the unlock RPC task on the NFS UOC rpc_waitqueue.

For NFSv3, use lockd's new nlmclnt_operations along with
nfs_async_iocounter_wait to defer NLM's unlock task until the lock
context's iocounter reaches zero.

For NFSv4, call nfs_async_iocounter_wait() directly from unlock's
current rpc_call_prepare.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
fs/nfs/file.c
fs/nfs/nfs3proc.c
fs/nfs/nfs4proc.c