dm snapshot: use barrier when writing exception store

Send barrier requests when updating the exception area.

Exception area updates need to be ordered w.r.t. data writes, so that
the writes are not reordered in hardware disk cache.

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 2662a41..6e3fe4f 100644 (file)
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -636,7 +636,7 @@ static void persistent_commit_exception(struct dm_exception_store *store,
        /*
         * Commit exceptions to disk.
         */
-       if (ps->valid && area_io(ps, WRITE))
+       if (ps->valid && area_io(ps, WRITE_BARRIER))
                ps->valid = 0;
 
        /*