[PATCH 3.16.y-ckt 061/216] dm cache: dirty flag was mistakenly being cleared when promoting via overwrite

[Luis Henriques]

3.16.7-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Thornber <ejt at redhat.com>

commit 1e32134a5a404e80bfb47fad8a94e9bbfcbdacc5 upstream.

If the incoming bio is a WRITE and completely covers a block then we
don't bother to do any copying for a promotion operation.  Once this is
done the cache block and origin block will be different, so we need to
set it to 'dirty'.

Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/dm-cache-target.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index e5bb12810ccc..e5308b8b4043 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -929,10 +929,14 @@ static void migration_success_post_commit(struct dm_cache_migration *mg)
 		}
 
 	} else {
-		clear_dirty(cache, mg->new_oblock, mg->cblock);
-		if (mg->requeue_holder)
+		if (mg->requeue_holder) {
+			clear_dirty(cache, mg->new_oblock, mg->cblock);
 			cell_defer(cache, mg->new_ocell, true);
-		else {
+		} else {
+			/*
+			 * The block was promoted via an overwrite, so it's dirty.
+			 */
+			set_dirty(cache, mg->new_oblock, mg->cblock);
 			bio_endio(mg->new_ocell->holder, 0);
 			cell_defer(cache, mg->new_ocell, false);
 		}
-- 
2.1.4