dm: limit the max bio size as BIO_MAX_PAGES * PAGE_SIZE

For BIO based DM, some targets aren't ready for dealing with bigger
incoming bio than 1Mbyte, such as crypt target.

Cc: Mike Snitzer <snitzer@redhat.com>
Cc:dm-devel@redhat.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index de17b7193299..7475739fee49 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -920,7 +920,15 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
                 return -EINVAL;
         }
 
-        ti->max_io_len = (uint32_t) len;
+        /*
+         * BIO based queue uses its own splitting. When multipage bvecs
+         * is switched on, size of the incoming bio may be too big to
+         * be handled in some targets, such as crypt.
+         *
+         * When these targets are ready for the big bio, we can remove
+         * the limit.
+         */
+        ti->max_io_len = min_t(uint32_t, len, BIO_MAX_PAGES * PAGE_SIZE);
 
         return 0;
 }