linux-kernel - [PATCH 09/13] blk-mq: remove unnecessary error count and check in blk_mq_dispatch_rq

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Message-Id: <20221223125223.1687670-10-shikemeng@huaweicloud.com>
Date:   Fri, 23 Dec 2022 20:52:19 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     axboe@...nel.dk, dwagner@...e.de, hare@...e.de,
        ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     hch@....de, john.garry@...wei.com, shikemeng@...weicloud.com
Subject: [PATCH 09/13] blk-mq: remove unnecessary error count and check in blk_mq_dispatch_rq_list

blk_mq_dispatch_rq_list will notify if hctx is busy in return bool. It will
return true if we are not busy and can handle more and return false on the
opposite. Inside blk_mq_dispatch_rq_list, we will return true if list is
empty and (errors + queued) != 0.

For busy error BLK_STS*_RESOURCE, the failed request will be added back
to list and list will not be empty. We count queued for BLK_STS_OK and
errors for rest error except busy error.
So if list is empty, (errors + queued) will be total requests in the list
which is checked not empty at beginning of blk_mq_dispatch_rq_list. So
(errors + queued) != 0 is always met if all requests are handled. Then the
(errors + queued) != 0 check and errors number count is not needed.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 block/blk-mq.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9c5971b04adc..97e2a07062de 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2009,7 +2009,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 	enum prep_dispatch prep;
 	struct request_queue *q = hctx->queue;
 	struct request *rq, *nxt;
-	int errors, queued;
+	int queued;
 	blk_status_t ret = BLK_STS_OK;
 	LIST_HEAD(zone_list);
 	bool needs_resource = false;
@@ -2020,7 +2020,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 	/*
 	 * Now process all the entries, sending them to the driver.
 	 */
-	errors = queued = 0;
+	queued = 0;
 	do {
 		struct blk_mq_queue_data bd;
 
@@ -2073,7 +2073,6 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 			needs_resource = true;
 			break;
 		default:
-			errors++;
 			blk_mq_end_request(rq, ret);
 		}
 	} while (!list_empty(list));
@@ -2151,10 +2150,10 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 
 		blk_mq_update_dispatch_busy(hctx, true);
 		return false;
-	} else
-		blk_mq_update_dispatch_busy(hctx, false);
+	}
 
-	return (queued + errors) != 0;
+	blk_mq_update_dispatch_busy(hctx, false);
+	return true;
 }
 
 /**
-- 
2.30.0