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>

diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 135c2f1..e4ecadf 100644 (file)
--- 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;