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From:   chengming.zhou@linux.dev
To:     axboe@kernel.dk, hch@lst.de, ming.lei@redhat.com,
        bvanassche@acm.org
Cc:     kbusch@kernel.org, mst@redhat.com,
        damien.lemoal@opensource.wdc.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, chengming.zhou@linux.dev,
        Chengming Zhou <zhouchengming@bytedance.com>
Subject: [PATCH v2 2/5] blk-mq: remove RQF_MQ_INFLIGHT
Date:   Wed, 13 Sep 2023 15:16:13 +0000
Message-Id: <20230913151616.3164338-3-chengming.zhou@linux.dev>
In-Reply-To: <20230913151616.3164338-1-chengming.zhou@linux.dev>
References: <20230913151616.3164338-1-chengming.zhou@linux.dev>
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From: Chengming Zhou <zhouchengming@bytedance.com>

Since the previous patch change to only account active requests when
we really allocate the driver tag, the RQF_MQ_INFLIGHT can be removed
and no double account problem.

1. none elevator: flush request will use the first pending request's
   driver tag, won't double account.

2. other elevator: flush request will be accounted when allocate driver
   tag when issue, and will be unaccounted when it put the driver tag.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
 block/blk-flush.c      | 11 ++---------
 block/blk-mq-debugfs.c |  1 -
 block/blk-mq.c         |  4 ----
 include/linux/blk-mq.h |  2 --
 4 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index e73dc22d05c1..3f4d41952ef2 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -323,16 +323,9 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
 	flush_rq->mq_ctx = first_rq->mq_ctx;
 	flush_rq->mq_hctx = first_rq->mq_hctx;
 
-	if (!q->elevator) {
+	if (!q->elevator)
 		flush_rq->tag = first_rq->tag;
-
-		/*
-		 * We borrow data request's driver tag, so have to mark
-		 * this flush request as INFLIGHT for avoiding double
-		 * account of this driver tag
-		 */
-		flush_rq->rq_flags |= RQF_MQ_INFLIGHT;
-	} else
+	else
 		flush_rq->internal_tag = first_rq->internal_tag;
 
 	flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index c3b5930106b2..5cbeb9344f2f 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -246,7 +246,6 @@ static const char *const rqf_name[] = {
 	RQF_NAME(STARTED),
 	RQF_NAME(FLUSH_SEQ),
 	RQF_NAME(MIXED_MERGE),
-	RQF_NAME(MQ_INFLIGHT),
 	RQF_NAME(DONTPREP),
 	RQF_NAME(SCHED_TAGS),
 	RQF_NAME(USE_SCHED),
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e776388decc3..c209a7dddee3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1066,10 +1066,6 @@ static inline void blk_mq_flush_tag_batch(struct blk_mq_hw_ctx *hctx,
 {
 	struct request_queue *q = hctx->queue;
 
-	/*
-	 * All requests should have been marked as RQF_MQ_INFLIGHT, so
-	 * update hctx->nr_active in batch
-	 */
 	blk_mq_sub_active_requests(hctx, nr_tags);
 
 	blk_mq_put_tags(hctx->tags, tag_array, nr_tags);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 958ed7e89b30..1ab3081c82ed 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -32,8 +32,6 @@ typedef __u32 __bitwise req_flags_t;
 #define RQF_FLUSH_SEQ		((__force req_flags_t)(1 << 4))
 /* merge of different types, fail separately */
 #define RQF_MIXED_MERGE		((__force req_flags_t)(1 << 5))
-/* track inflight for MQ */
-#define RQF_MQ_INFLIGHT		((__force req_flags_t)(1 << 6))
 /* don't call prep for this one */
 #define RQF_DONTPREP		((__force req_flags_t)(1 << 7))
 /* use hctx->sched_tags */
-- 
2.40.1