rbd: fix buffer size for writes to images with snapshots

commit 03507db631c94a48e316c7f638ffb2991544d617 upstream.

rbd_osd_req_create() needs to know the snapshot context size to create
a buffer large enough to send it with the message front. It gets this
from the img_request, which was not set for the obj_request yet. This
resulted in trying to write past the end of the front payload, hitting
this BUG:

libceph: BUG_ON(p > msg->front.iov_base + msg->front.iov_len);

Fix this by associating the obj_request with its img_request
immediately after it's created, before the osd request is created.

Fixes: http://tracker.ceph.com/issues/5760
Suggested-by: Alex Elder <alex.elder@linaro.org>
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Alex Elder <alex.elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 10c45e101c97..bb9948725973 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2213,6 +2213,11 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
                 rbd_segment_name_free(object_name);
                 if (!obj_request)
                         goto out_unwind;
+                /*
+                 * set obj_request->img_request before creating the
+                 * osd_request so that it gets the right snapc
+                 */
+                rbd_img_obj_request_add(img_request, obj_request);
 
                 if (type == OBJ_REQUEST_BIO) {
                         unsigned int clone_size;
@@ -2254,11 +2259,6 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
                                         obj_request->pages, length,
                                         offset & ~PAGE_MASK, false, false);
 
-                /*
-                 * set obj_request->img_request before formatting
-                 * the osd_request so that it gets the right snapc
-                 */
-                rbd_img_obj_request_add(img_request, obj_request);
                 if (write_request)
                         rbd_osd_req_format_write(obj_request);
                 else