afs: Retry unlock after afs_StoreAllSegments

HandleFlock calls afs_StoreAllSegments when unlocking an exclusive
flock lock. This can drop the write lock on avc, so we must
effectively retry the entire lock operation again, since the world may
have changed while we were waiting to reacquire the lock on avc. So,
retry once all of the lock checks up to that point, to ensure that a
lock on the file actually still exists.

FIXES 125446

Reviewed-on: http://gerrit.openafs.org/4393
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 601fcf1d7f7c88cfc0ffd877c5458340b3e59098)

Change-Id: Ibd215d586485d8f18f77665f5f85e6bee579e35e
Reviewed-on: http://gerrit.openafs.org/5766
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>

diff --git a/src/afs/VNOPS/afs_vnop_flock.c b/src/afs/VNOPS/afs_vnop_flock.c
index 2eeb427c3f4fb1b09aab44240cd1ebf84ff81a8a..33c679fef8c181d5bea50c99b80474dc7e72f64b 100644 (file)
--- a/src/afs/VNOPS/afs_vnop_flock.c
+++ b/src/afs/VNOPS/afs_vnop_flock.c
@@ -271,6 +271,8 @@ HandleFlock(struct vcache *avc, int acom, struct vrequest *areq,
 #endif
     ObtainWriteLock(&avc->lock, 118);
     if (acom & LOCK_UN) {
+       int stored_segments = 0;
+     retry_unlock:
 
 /* defect 3083 */
 
@@ -317,7 +319,14 @@ HandleFlock(struct vcache *avc, int acom, struct vrequest *areq,
                }
            }
        } else if (avc->flockCount == -1) {
-           afs_StoreAllSegments(avc, areq, AFS_SYNC | AFS_VMSYNC);     /* fsync file early */
+           if (!stored_segments) {
+               afs_StoreAllSegments(avc, areq, AFS_SYNC | AFS_VMSYNC); /* fsync file early */
+               /* afs_StoreAllSegments can drop and reacquire the write lock
+                * on avc and GLOCK, so the flocks may be completely different
+                * now. Go back and perform all checks again. */
+                stored_segments = 1;
+                goto retry_unlock;
+           }
            avc->flockCount = 0;
            /* And remove the (only) exclusive lock entry from the list... */
            osi_FreeSmallSpace(avc->slocks);