From: Mikulas Patocka <[email-masked]>

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 <[email-masked]>
Signed-off-by: Alasdair G Kergon <[email-masked]>

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

Index: linux-2.6.30/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-2.6.30.orig/drivers/md/dm-snap-persistent.c
+++ linux-2.6.30/drivers/md/dm-snap-persistent.c
@@ -636,7 +636,7 @@ static void persistent_commit_exception(
 	/*
 	 * Commit exceptions to disk.
 	 */
-	if (ps->valid && area_io(ps, WRITE))
+	if (ps->valid && area_io(ps, WRITE_BARRIER))
 		ps->valid = 0;
 
 	/*