linux-kernel - [PATCH v1 1/1] nvme: complete directly for hctx with only one ctx mapping

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Date:   Tue, 30 May 2023 10:41:19 +0800
From:   Po-Wen Kao <powen.kao@...iatek.com>
To:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, Jens Axboe <axboe@...nel.dk>,
        Keith Busch <kbusch@...nel.org>,
        "Christoph Hellwig" <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
CC:     <wsd_upstream@...iatek.com>, <peter.wang@...iatek.com>,
        <stanley.chu@...iatek.com>, <powen.kao@...iatek.com>,
        <alice.chao@...iatek.com>, <naomi.chu@...iatek.com>,
        <chun-hung.wu@...iatek.com>, <cc.chou@...iatek.com>,
        <eddie.huang@...iatek.com>, Ed Tsai <ed.tsai@...iatek.com>,
        <linux-block@...r.kernel.org>, <linux-nvme@...ts.infradead.org>
Subject: [PATCH v1 1/1] nvme: complete directly for hctx with only one ctx mapping

From: Ed Tsai <ed.tsai@...iatek.com>

Refer to
commit f168420c62e7
("blk-mq: don't redirect completion for hctx withs only one ctx mapping")
When nvme applies a 1:1 mapping of hctx and ctx, there will be no remote
request.

But for ufs, the submission and completion queue could be asymmetric.
(e.g. Multiple SQs share one CQ) Therefore, 1:1 mapping of hctx and
ctx won't complete request on the submission cpu. In this situation,
put this condition in block layer could violate the
QUEUE_FLAG_SAME_FORCE, as a result, move this back to nvme.

Signed-off-by: Ed Tsai <ed.tsai@...iatek.com>
Signed-off-by: Po-Wen Kao <powen.kao@...iatek.com>
---
 block/blk-mq.c           | 8 +++-----
 drivers/nvme/host/nvme.h | 4 ++++
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1749f5890606..b60c78f5ad46 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1181,12 +1181,10 @@ bool blk_mq_complete_request_remote(struct request *rq)
 	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 
 	/*
-	 * For request which hctx has only one ctx mapping,
-	 * or a polled request, always complete locally,
-	 * it's pointless to redirect the completion.
+	 * For a polled request, always complete locally, it's pointless
+	 * to redirect the completion.
 	 */
-	if (rq->mq_hctx->nr_ctx == 1 ||
-		rq->cmd_flags & REQ_POLLED)
+	if (rq->cmd_flags & REQ_POLLED)
 		return false;
 
 	if (blk_mq_complete_need_ipi(rq)) {
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 7cf8e44d135e..acc9b1ce071d 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -702,6 +702,10 @@ static inline bool nvme_try_complete_req(struct request *req, __le16 status,
 	nvme_should_fail(req);
 	if (unlikely(blk_should_fake_timeout(req->q)))
 		return true;
+	if (likely(req->mq_hctx->nr_ctx == 1)) {
+		WRITE_ONCE(req->state, MQ_RQ_COMPLETE);
+		return false;
+	}
 	return blk_mq_complete_request_remote(req);
 }
 
-- 
2.18.0