[PATCH] rbd: zero return code in rbd_dev_image_id()

[Alex Elder <elder@inktank.com>]

There is a call in rbd_dev_image_id() to rbd_req_sync_exec()
to get the image id for an image.  Despite the "get_id" class
method only returning 0 on success, I am getting back a positive
value (I think the number of bytes returned with the call).

That may or may not be how rbd_req_sync_exec() is supposed to
behave, but zeroing the return value if successful makes it moot
and makes this path through the code work as desired.

Do the same in rbd_dev_v2_object_prefix().

Signed-off-by: Alex Elder <elder@inktank.com>
---
 drivers/block/rbd.c |    2 ++
 1 file changed, 2 insertions(+)

Index: b/drivers/block/rbd.c
===================================================================
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2207,6 +2207,7 @@ static int rbd_dev_v2_object_prefix(stru
 	dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
 	if (ret < 0)
 		goto out;
+	ret = 0;    /* rbd_req_sync_exec() can return positive */

 	p = reply_buf;
 	rbd_dev->header.object_prefix = ceph_extract_encoded_string(&p,
@@ -2900,6 +2901,7 @@ static int rbd_dev_image_id(struct rbd_d
 	dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
 	if (ret < 0)
 		goto out;
+	ret = 0;    /* rbd_req_sync_exec() can return positive */

 	p = response;
 	rbd_dev->image_id = ceph_extract_encoded_string(&p,