[PATCH 3.16.y-ckt 060/216] dm cache: only use overwrite optimisation for promotion when in writeback mode

Luis Henriques
2015-01-12T18:23:42Z

From: Joe Thornber <ejt@redhat.com>

commit f29a3147e251d7ae20d3194ff67f109d71e501b4 upstream.

Overwrite causes the cache block and origin blocks to diverge, which
is only allowed in writeback mode.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
drivers/md/dm-cache-target.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index c892e48655c2..e5bb12810ccc 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1043,7 +1043,8 @@ static void issue_copy(struct dm_cache_migration *mg)

avoid = is_discarded_oblock(cache, mg->new_oblock);

- if (!avoid && bio_writes_complete_block(cache, bio)) {
+ if (writeback_mode(&cache->features) &&
+ !avoid && bio_writes_complete_block(cache, bio)) {
issue_overwrite(mg, bio);
return;
}
--
2.1.4