linux-kernel - [PATCH 2/3] block: factor out blk_mq_dispatch_queue

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Message-ID: <20250423205127.2976981-3-csander@purestorage.com>
Date: Wed, 23 Apr 2025 14:51:26 -0600
From: Caleb Sander Mateos <csander@...estorage.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Caleb Sander Mateos <csander@...estorage.com>
Subject: [PATCH 2/3] block: factor out blk_mq_dispatch_queue_requests() helper

Factor out the logic from blk_mq_flush_plug_list() that calls
->queue_rqs() with a fallback to ->queue_rq() into a helper function
blk_mq_dispatch_queue_requests(). This is in preparation for using this
code with other lists of requests.

Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
---
 block/blk-mq.c | 43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index fb514fd41d76..a777cb361ee3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2834,10 +2834,31 @@ static void __blk_mq_flush_list(struct request_queue *q, struct rq_list *rqs)
 	if (blk_queue_quiesced(q))
 		return;
 	q->mq_ops->queue_rqs(rqs);
 }
 
+static void blk_mq_dispatch_queue_requests(struct rq_list *rqs, unsigned depth)
+{
+	struct request_queue *q = rq_list_peek(rqs)->q;
+
+	trace_block_unplug(q, depth, true);
+
+	/*
+	 * Peek first request and see if we have a ->queue_rqs() hook.
+	 * If we do, we can dispatch the whole 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.
+	 */
+	if (q->mq_ops->queue_rqs) {
+		blk_mq_run_dispatch_ops(q, __blk_mq_flush_list(q, rqs));
+		if (rq_list_empty(rqs))
+			return;
+	}
+
+	blk_mq_run_dispatch_ops(q, blk_mq_issue_direct(rqs));
+}
+
 static void blk_mq_dispatch_list(struct rq_list *rqs, bool from_sched)
 {
 	struct blk_mq_hw_ctx *this_hctx = NULL;
 	struct blk_mq_ctx *this_ctx = NULL;
 	struct rq_list requeue_list = {};
@@ -2881,11 +2902,10 @@ static void blk_mq_dispatch_list(struct rq_list *rqs, bool from_sched)
 	percpu_ref_put(&this_hctx->queue->q_usage_counter);
 }
 
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
-	struct request *rq;
 	unsigned int depth;
 
 	/*
 	 * We may have been called recursively midway through handling
 	 * plug->mq_list via a schedule() in the driver's queue_rq() callback.
@@ -2897,30 +2917,11 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 		return;
 	depth = plug->rq_count;
 	plug->rq_count = 0;
 
 	if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
-		struct request_queue *q;
-
-		rq = rq_list_peek(&plug->mq_list);
-		q = rq->q;
-		trace_block_unplug(q, depth, true);
-
-		/*
-		 * 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.
-		 */
-		if (q->mq_ops->queue_rqs) {
-			blk_mq_run_dispatch_ops(q,
-				__blk_mq_flush_list(q, &plug->mq_list));
-			if (rq_list_empty(&plug->mq_list))
-				return;
-		}
-
-		blk_mq_run_dispatch_ops(q, blk_mq_issue_direct(&plug->mq_list));
+		blk_mq_dispatch_queue_requests(&plug->mq_list, depth);
 		if (rq_list_empty(&plug->mq_list))
 			return;
 	}
 
 	do {
-- 
2.45.2