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From:   Kemeng Shi <shikemeng@huaweicloud.com>
To:     hch@lst.de, axboe@kernel.dk, dwagner@suse.de, hare@suse.de,
        ming.lei@redhat.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     john.garry@huawei.com, jack@suse.cz
Subject: [PATCH v4 08/14] blk-mq: remove unncessary error count and commit in blk_mq_plug_issue_direct
Date:   Wed, 18 Jan 2023 17:37:20 +0800
Message-Id: <20230118093726.3939160-8-shikemeng@huaweicloud.com>
In-Reply-To: <20230118093726.3939160-1-shikemeng@huaweicloud.com>
References: <20230118093726.3939160-1-shikemeng@huaweicloud.com>
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We need only to explicitly commit in two error cases:
 -did not queue everything initially scheduled to queue
 -the last attempt to queue a request failed
(see comment of blk_mq_commit_rqs for more details).
Both cases can be checked with ret of last request which breaks list walk.
Remove unnecessary error count and unnecessary commit triggered by error
which is not covered by cases described above.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 block/blk-mq.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 159d9163c46c..4066fe5c3147 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2700,11 +2700,10 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
 	struct blk_mq_hw_ctx *hctx = NULL;
 	struct request *rq;
 	int queued = 0;
-	int errors = 0;
+	blk_status_t ret = BLK_STS_OK;
 
 	while ((rq = rq_list_pop(&plug->mq_list))) {
 		bool last = rq_list_empty(plug->mq_list);
-		blk_status_t ret;
 
 		if (hctx != rq->mq_hctx) {
 			if (hctx) {
@@ -2722,20 +2721,15 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
 		case BLK_STS_RESOURCE:
 		case BLK_STS_DEV_RESOURCE:
 			blk_mq_request_bypass_insert(rq, false, true);
-			blk_mq_commit_rqs(hctx, queued, false);
-			return;
+			goto out;
 		default:
 			blk_mq_end_request(rq, ret);
-			errors++;
 			break;
 		}
 	}
 
-	/*
-	 * If we didn't flush the entire list, we could have told the driver
-	 * there was more coming, but that turned out to be a lie.
-	 */
-	if (errors)
+out:
+	if (ret != BLK_STS_OK)
 		blk_mq_commit_rqs(hctx, queued, false);
 }
 
-- 
2.30.0