4 files changed, 23 insertions, 14 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index fcc0e893d687..c27613de80c5 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -201,15 +201,22 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 	 * leave them there for as long as we can. Mark the hw queue as
 	 * needing a restart in that case.
 	 */
-	if (list_empty(&rq_list)) {
-		if (e && e->type->ops.mq.dispatch_requests)
-			e->type->ops.mq.dispatch_requests(hctx, &rq_list);
-		else
-			blk_mq_flush_busy_ctxs(hctx, &rq_list);
-	} else
+	if (!list_empty(&rq_list)) {
 		blk_mq_sched_mark_restart(hctx);
-
-	blk_mq_dispatch_rq_list(hctx, &rq_list);
+		blk_mq_dispatch_rq_list(hctx, &rq_list);
+	} else if (!e || !e->type->ops.mq.dispatch_request) {
+		blk_mq_flush_busy_ctxs(hctx, &rq_list);
+		blk_mq_dispatch_rq_list(hctx, &rq_list);
+	} else {
+		do {
+			struct request *rq;
+
+			rq = e->type->ops.mq.dispatch_request(hctx);
+			if (!rq)
+				break;
+			list_add(&rq->queuelist, &rq_list);
+		} while (blk_mq_dispatch_rq_list(hctx, &rq_list));
+	}
 }
 
 void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 21795c6575bc..301ae29fd229 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -998,7 +998,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
 	 */
 	if (!list_empty(list)) {
 		spin_lock(&hctx->lock);
-		list_splice(list, &hctx->dispatch);
+		list_splice_init(list, &hctx->dispatch);
 		spin_unlock(&hctx->lock);
 
 		/*
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index a01986d7b6fb..d93ec713fa62 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -287,14 +287,16 @@ done:
 	return rq;
 }
 
-static void dd_dispatch_requests(struct blk_mq_hw_ctx *hctx,
-				 struct list_head *rq_list)
+static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
 {
 	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
+	struct request *rq;
 
 	spin_lock(&dd->lock);
-	blk_mq_sched_move_to_dispatch(hctx, rq_list, __dd_dispatch_request);
+	rq = __dd_dispatch_request(hctx);
 	spin_unlock(&dd->lock);
+
+	return rq;
 }
 
 static void dd_exit_queue(struct elevator_queue *e)
@@ -517,7 +519,7 @@ static struct elv_fs_entry deadline_attrs[] = {
 static struct elevator_type mq_deadline = {
 	.ops.mq = {
 		.insert_requests	= dd_insert_requests,
-		.dispatch_requests	= dd_dispatch_requests,
+		.dispatch_request	= dd_dispatch_request,
 		.next_request		= elv_rb_latter_request,
 		.former_request		= elv_rb_former_request,
 		.bio_merge		= dd_bio_merge,
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index ecb96fd67c6d..b5825c4f06f7 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -92,7 +92,7 @@ struct elevator_mq_ops {
 	struct request *(*get_request)(struct request_queue *, unsigned int, struct blk_mq_alloc_data *);
 	void (*put_request)(struct request *);
 	void (*insert_requests)(struct blk_mq_hw_ctx *, struct list_head *, bool);
-	void (*dispatch_requests)(struct blk_mq_hw_ctx *, struct list_head *);
+	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
 	bool (*has_work)(struct blk_mq_hw_ctx *);
 	void (*completed_request)(struct blk_mq_hw_ctx *, struct request *);
 	void (*started_request)(struct request *);