From: Heinz Mauelshagen <[email protected]>

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

===============

commit f1daa838e861ae1a0fb7cd9721a21258430fcc8c upstream.

The DM cache target cannot cope with discards that span multiple cache
blocks, so each discard bio that spans more than one cache block must
get split by the DM core.

Signed-off-by: Heinz Mauelshagen <[email protected]>
Acked-by: Joe Thornber <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
 drivers/md/dm-cache-target.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index d64bf7d6c8fe..0cf3700bfe9e 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1932,6 +1932,8 @@ static int cache_create(struct cache_args *ca, struct 
cache **result)
        ti->num_discard_bios = 1;
        ti->discards_supported = true;
        ti->discard_zeroes_data_unsupported = true;
+       /* Discard bios must be split on a block boundary */
+       ti->split_discard_bios = true;
 
        cache->features = ca->features;
        ti->per_bio_data_size = get_per_bio_data_size(cache);
-- 
2.0.0

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