drbd: always use_bmbv, ignore setting

Now that the peer may handle multi-bio EEs,
we can ignore the peer's limit,
and concentrate on the limits of the local IO stack.

This is safe accross drbd protocol versions,
as our queue_max_sectors() will be adjusted accordingly.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_nl.c

@@ -704,9 +704,6 @@ void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __mu
 	struct request_queue * const b = mdev->ldev->backing_bdev->bd_disk->queue;
 	int max_segments = mdev->ldev->dc.max_bio_bvecs;
 
-	if (b->merge_bvec_fn && !mdev->ldev->dc.use_bmbv)
-		max_seg_s = PAGE_SIZE;
-
 	max_seg_s = min(queue_max_sectors(b) * queue_logical_block_size(b), max_seg_s);
 
 	blk_queue_max_hw_sectors(q, max_seg_s >> 9);

drivers/block/drbd/drbd_receiver.c

@@ -3011,7 +3011,11 @@ static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
 			ldsc = 1;
 		}
 
+		if (mdev->agreed_pro_version < 94)
 			max_seg_s = be32_to_cpu(p->max_segment_size);
+		else /* drbd 8.3.8 onwards */
+			max_seg_s = DRBD_MAX_SEGMENT_SIZE;
+
 		if (max_seg_s != queue_max_segment_size(mdev->rq_queue))
 			drbd_setup_queue_param(mdev, max_seg_s);
 

drivers/block/drbd/drbd_req.c

@@ -1110,7 +1110,7 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	} else if (limit && get_ldev(mdev)) {
 		struct request_queue * const b =
 			mdev->ldev->backing_bdev->bd_disk->queue;
-		if (b->merge_bvec_fn && mdev->ldev->dc.use_bmbv) {
+		if (b->merge_bvec_fn) {
 			backing_limit = b->merge_bvec_fn(b, bvm, bvec);
 			limit = min(limit, backing_limit);
 		}