linux-kernel - [PATCH 06/16] blk-mq: cleanup shared tags case in blk_mq_update_nr

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Message-Id: <20250814033522.770575-7-yukuai1@huaweicloud.com>
Date: Thu, 14 Aug 2025 11:35:12 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: axboe@...nel.dk,
	yukuai3@...wei.com,
	bvanassche@....org,
	nilay@...ux.ibm.com,
	hare@...e.de,
	ming.lei@...hat.com
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH 06/16] blk-mq: cleanup shared tags case in blk_mq_update_nr_requests()

From: Yu Kuai <yukuai3@...wei.com>

For shared tags case, all hctx->shared_tags/tags are the same, it
doesn't make sense to call blk_mq_tag_update_depth() multiple times
for the same tags.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-mq-tag.c |  7 -------
 block/blk-mq.c     | 40 +++++++++++++++++++++-------------------
 2 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 7613a9889eb1..84a452e708e4 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -596,13 +596,6 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		struct blk_mq_tag_set *set = hctx->queue->tag_set;
 		struct blk_mq_tags *new;
 
-		/*
-		 * Only the sbitmap needs resizing since we allocated the max
-		 * initially.
-		 */
-		if (blk_mq_is_shared_tags(set->flags))
-			return 0;
-
 		new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
 		if (!new)
 			return -ENOMEM;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 14446d3927dd..c29f98ec283d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4926,32 +4926,34 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 
 	blk_mq_quiesce_queue(q);
 
-	queue_for_each_hw_ctx(q, hctx, i) {
-		/*
-		 * If we're using an MQ scheduler, just update the scheduler
-		 * queue depth. This is similar to what the old code would do.
-		 */
-		if (hctx->sched_tags)
-			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
-						      nr);
-		else
-			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr);
-
-		if (ret)
-			goto out;
-	}
-
-	q->nr_requests = nr;
-	if (q->elevator && q->elevator->type->ops.depth_updated)
-		q->elevator->type->ops.depth_updated(q);
-
 	if (blk_mq_is_shared_tags(set->flags)) {
 		if (q->elevator)
 			blk_mq_tag_update_sched_shared_tags(q);
 		else
 			blk_mq_tag_resize_shared_tags(set, nr);
+	} else {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			/*
+			 * If we're using an MQ scheduler, just update the
+			 * scheduler queue depth. This is similar to what the
+			 * old code would do.
+			 */
+			if (hctx->sched_tags)
+				ret = blk_mq_tag_update_depth(hctx,
+						&hctx->sched_tags, nr);
+			else
+				ret = blk_mq_tag_update_depth(hctx,
+						&hctx->tags, nr);
+
+			if (ret)
+				goto out;
+		}
 	}
 
+	q->nr_requests = nr;
+	if (q->elevator && q->elevator->type->ops.depth_updated)
+		q->elevator->type->ops.depth_updated(q);
+
 out:
 	blk_mq_unquiesce_queue(q);
 	return ret;
-- 
2.39.2