rbd: allow null image name
We will know the image id for format 2 parent images, but won't
initially know its image name. Avoid making the query for an image
id in rbd_dev_image_id() if it's already known.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 8d26c0f..a852133 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3068,6 +3068,14 @@
void *p;
/*
+ * When probing a parent image, the image id is already
+ * known (and the image name likely is not). There's no
+ * need to fetch the image id again in this case.
+ */
+ if (rbd_dev->spec->image_id)
+ return 0;
+
+ /*
* First, see if the format 2 image id file exists, and if
* so, get the image's persistent id from it.
*/