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| author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-02-04 20:17:49 -0500 |
|---|---|---|
| committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2013-02-11 15:33:12 -0500 |
| commit | 9a99af494bd7141d567d00b5ef94b141821e158c (patch) | |
| tree | 1ca9c1ea6536b5384012e50d889eeb7753460244 /fs/nfs | |
| parent | c137afabe330f64eddcd4dd281258807e27fd430 (diff) | |
| download | linux-9a99af494bd7141d567d00b5ef94b141821e158c.tar.bz2 | |
NFSv4.1: Prevent deadlocks between state recovery and file locking
We currently have a deadlock in which the state recovery thread
ends up blocking due to one of the locks which it is trying to
recover holding the nfs_inode->rwsem.
The situation is as follows: the state recovery thread is
scheduled in order to recover from a reboot. It immediately
drains the session, forcing all ordinary NFSv4.1 calls to
nfs41_setup_sequence() to be put to sleep. This includes the
file locking process that holds the nfs_inode->rwsem.
When the thread gets to nfs4_reclaim_locks(), it tries to
grab a write lock on nfs_inode->rwsem, and boom...
Fix is to have the lock drop the nfs_inode->rwsem while it is
doing RPC calls. We use a sequence lock in order to signal to
the locking process whether or not a state recovery thread has
run on that inode, in which case it should retry the lock.
Reported-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs')
| -rw-r--r-- | fs/nfs/nfs4proc.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 62fa4001e47a..92584c1ea725 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -4813,8 +4813,10 @@ static int nfs41_lock_expired(struct nfs4_state *state, struct file_lock *reques static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock *request) { + struct nfs4_state_owner *sp = state->owner; struct nfs_inode *nfsi = NFS_I(state->inode); unsigned char fl_flags = request->fl_flags; + unsigned int seq; int status = -ENOLCK; if ((fl_flags & FL_POSIX) && @@ -4836,9 +4838,16 @@ static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock status = do_vfs_lock(request->fl_file, request); goto out_unlock; } + seq = raw_seqcount_begin(&sp->so_reclaim_seqcount); + up_read(&nfsi->rwsem); status = _nfs4_do_setlk(state, cmd, request, NFS_LOCK_NEW); if (status != 0) + goto out; + down_read(&nfsi->rwsem); + if (read_seqcount_retry(&sp->so_reclaim_seqcount, seq)) { + status = -NFS4ERR_DELAY; goto out_unlock; + } /* Note: we always want to sleep here! */ request->fl_flags = fl_flags | FL_SLEEP; if (do_vfs_lock(request->fl_file, request) < 0) |