drbd: merge_bvec_fn: properly remap bvm->bi_bdev
This was not noticed for many years. Affects operation if
md raid is used a backing device for DRBD.
CC: stable@kernel.org # v3.2+
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>
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 5a01c53..90319b1 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1545,6 +1545,7 @@
struct request_queue * const b =
device->ldev->backing_bdev->bd_disk->queue;
if (b->merge_bvec_fn) {
+ bvm->bi_bdev = device->ldev->backing_bdev;
backing_limit = b->merge_bvec_fn(b, bvm, bvec);
limit = min(limit, backing_limit);
}