dm cache: always split discards on cache block boundaries

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 <heinzm@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 9306e0bcb5647b047b9b5bddd50dde28baa7238f..c0ad90d91252974ad43a5c95456d5914d7fc9692 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2195,6 +2195,8 @@ 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);