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>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index de17b71..7475739 100644 (file)
--- 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;
 }