dm: limit the max bio size as BIO_MAX_PAGES * PAGE_SIZE

Ming Lei · axboe · commit 8f50e358153d · 2018-01-06T09:18:00.000-07:00
For BIO based DM, some targets aren't ready for dealing with bigger
incoming bio than 1Mbyte, such as crypt target.

Cc: Mike Snitzer &lt;snitzer@redhat.com&gt;
Cc:dm-devel@redhat.com
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Ming Lei &lt;ming.lei@redhat.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
diff --git 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;
 }
