drbd: merge_bvec_fn: properly remap bvm->bi_bdev

commit 3b9d35d744bb5139f9fed57f38c019bb8c7d351c upstream.

This was not noticed for many years. Affects operation if
md raid is used a backing device for DRBD.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
[bwh: Backported to 3.2: s/device/mdev/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index be984e0..43da226 100644 (file)
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1184,6 +1184,7 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
                struct request_queue * const b =
                        mdev->ldev->backing_bdev->bd_disk->queue;
                if (b->merge_bvec_fn) {
                struct request_queue * const b =
                        mdev->ldev->backing_bdev->bd_disk->queue;
                if (b->merge_bvec_fn) {

+                       bvm->bi_bdev = mdev->ldev->backing_bdev;

                        backing_limit = b->merge_bvec_fn(b, bvm, bvec);
                        limit = min(limit, backing_limit);
                }
                        backing_limit = b->merge_bvec_fn(b, bvm, bvec);
                        limit = min(limit, backing_limit);
                }