dm snapshot: flush disk cache when merging

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 135c2f1fdbf..e4ecadf0548 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -753,7 +753,7 @@ static int persistent_commit_merge(struct dm_exception_store *store,
         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;