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

[Mikulas Patocka <mpatocka redhat com>]

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 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;
 
 	/*