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From:   Ed Tsai <ed.tsai@mediatek.com>
To:     <axboe@kernel.dk>
CC:     <matthias.bgg@gmail.com>,
        <angelogioacchino.delregno@collabora.com>,
        <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>, <kbusch@kernel.org>,
        <amergnat@baylibre.com>, <liusong@linux.alibaba.com>,
        <wsd_upstream@mediatek.com>, <peter.wang@mediatek.com>,
        <stanley.chu@mediatek.com>, <powen.kao@mediatek.com>,
        <alice.chao@mediatek.com>, <naomi.chu@mediatek.com>,
        <Chun-Hung.Wu@mediatek.com>, Ed Tsai <ed.tsai@mediatek.com>
Subject: [PATCH v3] blk-mq: check on cpu id when there is only one ctx mapping
Date:   Wed, 14 Jun 2023 08:25:29 +0800
Message-ID: <20230614002529.6636-1-ed.tsai@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

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 queues 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,
this nr_ctx check could violate the QUEUE_FLAG_SAME_FORCE, as a result,
check on cpu id when there is only one ctx mapping.

Signed-off-by: Ed Tsai <ed.tsai@mediatek.com>
Signed-off-by: Po-Wen Kao <powen.kao@mediatek.com>
Suggested-by: Keith Busch <kbusch@kernel.org>

---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 41f7e2b500bd..ecc30ebe9483 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1176,7 +1176,8 @@ bool blk_mq_complete_request_remote(struct request *rq)
 	 * or a polled request, always complete locally,
 	 * it's pointless to redirect the completion.
 	 */
-	if (rq->mq_hctx->nr_ctx == 1 ||
+	if ((rq->mq_hctx->nr_ctx == 1 &&
+	     rq->mq_ctx->cpu == raw_smp_processor_id()) ||
 		rq->cmd_flags & REQ_POLLED)
 		return false;
 
-- 
2.18.0