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 1a75869d3a825dd646bec2940ffd4eea3d0435ad..677973641d2ba916e3128780192e2a21711eae81 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1954,6 +1954,8 @@ 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);