From: Mikulas Patocka <mpatocka@redhat.com>

This patch makes dm-snapshot flush disk cache when writing metadata for
merging snapshot.

Without cache flushing the disk may reorder metadata write and other
data writes and there is a possibility of data corruption in case of
power fault.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

---
 drivers/md/dm-snap-persistent.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-3.0/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-3.0.orig/drivers/md/dm-snap-persistent.c
+++ linux-3.0/drivers/md/dm-snap-persistent.c
@@ -753,7 +753,7 @@ static int persistent_commit_merge(struc
 	for (i = 0; i < nr_merged; i++)
 		clear_exception(ps, ps->current_committed - 1 - i);
 
-	r = area_io(ps, WRITE);
+	r = area_io(ps, WRITE_FLUSH_FUA);
 	if (r < 0)
 		return r;