loop: add error handling support for add_disk()

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -2394,13 +2394,19 @@ static int loop_add(int i)
 	disk->event_flags	= DISK_EVENT_FLAG_UEVENT;
 	sprintf(disk->disk_name, "loop%d", i);
 	/* Make this loop device reachable from pathname. */
-	add_disk(disk);
+	err = add_disk(disk);
+	if (err)
+		goto out_cleanup_disk;
+
 	/* Show this loop device. */
 	mutex_lock(&loop_ctl_mutex);
 	lo->idr_visible = true;
 	mutex_unlock(&loop_ctl_mutex);
+
 	return i;
 
+out_cleanup_disk:
+	blk_cleanup_disk(disk);
 out_cleanup_tags:
 	blk_mq_free_tag_set(&lo->tag_set);
 out_free_idr: