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>
[lizf: Backported to 3.4: s/device/mdev]
Signed-off-by: Zefan Li <lizefan@huawei.com>
1 file changed