[PATCH 1/6] rbd: skip getting image id if known

[Alex Elder <elder@inktank.com>]

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>
---
 drivers/block/rbd.c |    8 ++++++++
 1 file changed, 8 insertions(+)

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 @@ static int rbd_dev_image_id(struct rbd_device
*rbd_dev)
 	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.
 	 */
-- 
1.7.9.5