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

Change-Id: If249b0e761b595062068d7a506be85a3307870e8
Reviewed-on: http://gerrit.openafs.org/4393
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>

diff --git a/src/afs/VNOPS/afs_vnop_flock.c b/src/afs/VNOPS/afs_vnop_flock.c
index 931a72c..013c5dc 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);