> @@ -2208,6 +2208,19 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
> int queued = 0;
> int errors = 0;
>
> + /*
> + * Peek first request and see if we have a ->queue_rqs() hook. If we
> + * do, we can dispatch the whole plug list in one go. We already know
> + * at this point that all requests belong to the same queue, caller
> + * must ensure that's the case.
> + */
> + rq = rq_list_peek(&plug->mq_list);
> + if (rq->q->mq_ops->queue_rqs) {
> + rq->q->mq_ops->queue_rqs(&plug->mq_list);
> + if (rq_list_empty(plug->mq_list))
> + return;
> + }
I'd move this straight into the caller to simplify the follow, something
like the patch below. Also I wonder if the slow path might want to
be moved from blk_mq_flush_plug_list into a separate helper to keep
the fast path as straight as possible?
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3ab34c4f20daf..370f4b2ab4511 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2255,6 +2255,14 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
plug->rq_count = 0;
if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
+ struct request_queue *q = rq_list_peek(&plug->mq_list)->q;
+
+ if (q->mq_ops->queue_rqs) {
+ q->mq_ops->queue_rqs(&plug->mq_list);
+ if (rq_list_empty(plug->mq_list))
+ return;
+ }
+
blk_mq_plug_issue_direct(plug, false);
if (rq_list_empty(plug->mq_list))
return;
