[dm-devel] [PATCH 17/17] bottom-layer barrier support

[Mikulas Patocka]

dm-snapshot-sync-exception-store.patch

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 at redhat.com>

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

Index: linux-2.6.30-rc2-devel/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-2.6.30-rc2-devel.orig/drivers/md/dm-snap-persistent.c	2009-04-10 06:16:42.000000000 +0200
+++ linux-2.6.30-rc2-devel/drivers/md/dm-snap-persistent.c	2009-04-20 08:41:18.000000000 +0200
@@ -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;
 
 	/*