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Mon, 08 Dec 2025 03:02:21 -0800 (PST) Received: from localhost.localdomain ([116.128.244.171]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-349de99226esm3888102a91.13.2025.12.08.03.02.19 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 08 Dec 2025 03:02:21 -0800 (PST) From: chengkaitao To: axboe@kernel.dk Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Chengkaitao Subject: [PATCH] mq-deadline: the dd->dispatch queue follows a FIFO policy Date: Mon, 8 Dec 2025 19:02:13 +0800 Message-ID: <20251208110213.92884-1-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Chengkaitao In the initial implementation, the 'list_add(&rq->queuelist, ...' statement added to the dd_insert_request function was designed to differentiate priorities among various IO-requests within the same linked list. For example, 'Commit 945ffb60c11d ("mq-deadline: add blk-mq adaptation of the deadline IO scheduler")', introduced this 'list_add' operation to ensure that requests with the at_head flag would always be dispatched before requests without the REQ_TYPE_FS flag. Since 'Commit 7687b38ae470 ("bfq/mq-deadline: remove redundant check for passthrough request")', removed blk_rq_is_passthrough, the dd->dispatch list now contains only requests with the at_head flag. In this context, all at_head requests should be treated as having equal priority, and a first-in-first-out (FIFO) policy better aligns with the current situation. Therefore, replacing list_add with list_add_tail is more appropriate. Signed-off-by: Chengkaitao --- block/mq-deadline.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 3e3719093aec..dcd7f4f1ecd2 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -661,7 +661,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hct= x, struct request *rq, trace_block_rq_insert(rq); =20 if (flags & BLK_MQ_INSERT_AT_HEAD) { - list_add(&rq->queuelist, &dd->dispatch); + list_add_tail(&rq->queuelist, &dd->dispatch); rq->fifo_time =3D jiffies; } else { deadline_add_rq_rb(per_prio, rq); --=20 2.50.1 (Apple Git-155)