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authorTrond Myklebust <Trond.Myklebust@netapp.com>2013-02-04 20:17:49 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2013-02-11 15:33:12 -0500
commit9a99af494bd7141d567d00b5ef94b141821e158c (patch)
tree1ca9c1ea6536b5384012e50d889eeb7753460244 /fs
parentc137afabe330f64eddcd4dd281258807e27fd430 (diff)
downloadlinux-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')
-rw-r--r--fs/nfs/nfs4proc.c9
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)