dm table: an 'all_blk_mq' table must be loaded for a blk-mq DM device

When dm_table_set_type() is used by a target to establish a DM table's
type (e.g. DM_TYPE_MQ_REQUEST_BASED in the case of DM multipath) the
DM core must go on to verify that the devices in the table are
compatible with the established type.

Fixes: e83068a5 ("dm mpath: add optional "queue_mode" feature")
Cc: stable@vger.kernel.org # 4.8+
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-table.c

@@ -981,6 +981,11 @@ verify_rq_based:
 		t->all_blk_mq = true;
 	}
 
+	if (t->type == DM_TYPE_MQ_REQUEST_BASED && !t->all_blk_mq) {
+		DMERR("table load rejected: all devices are not blk-mq request-stackable");
+		return -EINVAL;
+	}
+
 	return 0;
 }