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authorBob Peterson <rpeterso@redhat.com>2013-04-25 12:49:17 -0400
committerSteven Whitehouse <swhiteho@redhat.com>2013-04-26 10:09:04 +0100
commit222cb538f5f18741466dc27cc6cf4375bccf1f89 (patch)
treea1cd04d4703bd7b436dce16e391012ef09e1e7fd
parent7bd8b2eb32c404ebe61986083ce02642b6ff3bf6 (diff)
downloadlinux-222cb538f5f18741466dc27cc6cf4375bccf1f89.tar.gz
GFS2: Flush work queue before clearing glock hash tables
There was a timing window when a GFS2 file system was unmounted that caused GFS2 to call BUG() and panic the kernel. The call to BUG() is meant to ensure that the glock reference count, gl_ref, never gets down to zero and bounce back up again. What was happening during umount is that function gfs2_put_super was dequeing its glocks for well-known files. In particular, we saw it on the journal glock, sd_jinode_gh. The dequeue caused delayed work to be queued for the glock state machine, to transition the lock to an "unlocked" state. While the work was still queued, gfs2_put_super called gfs2_gl_hash_clear to clear out the glock hash tables. If the timing was just so, the glock work function would drop the reference count at the time when it was being checked for zero, and that caused BUG() to be called. This patch calls flush_workqueue before clearing the glock hash tables, thereby ensuring that the delayed work is executed before the hash tables are cleared, and therefore the reference count never goes to zero until the glock is cleared. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
-rw-r--r--fs/gfs2/glock.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 3b9e1788ebf..b777691b1c2 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1577,6 +1577,7 @@ static void dump_glock_func(struct gfs2_glock *gl)
void gfs2_gl_hash_clear(struct gfs2_sbd *sdp)
{
set_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags);
+ flush_workqueue(glock_workqueue);
glock_hash_walk(clear_glock, sdp);
flush_workqueue(glock_workqueue);
wait_event(sdp->sd_glock_wait, atomic_read(&sdp->sd_glock_disposal) == 0);