linux-kernel - [PATCH for-6.18/block 06/10] blk-mq: split bitmap grow and resize case in blk_mq_update_nr

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Message-Id: <20250908061533.3062917-7-yukuai1@huaweicloud.com>
Date: Mon,  8 Sep 2025 14:15:29 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: nilay@...ux.ibm.com,
	ming.lei@...hat.com,
	axboe@...nel.dk
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH for-6.18/block 06/10] blk-mq: split bitmap grow and resize case in blk_mq_update_nr_requests()

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

No functional changes are intended, make code cleaner and prepare to fix
the grow case in following patches.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-mq.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1ff6370f7314..82fa81036115 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4931,21 +4931,25 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 			blk_mq_tag_update_sched_shared_tags(q);
 		else
 			blk_mq_tag_resize_shared_tags(set, nr);
-	} else {
+	} else if (!q->elevator) {
 		queue_for_each_hw_ctx(q, hctx, i) {
 			if (!hctx->tags)
 				continue;
-			/*
-			 * 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);
+			sbitmap_queue_resize(&hctx->tags->bitmap_tags,
+				nr - hctx->tags->nr_reserved_tags);
+		}
+	} else if (nr <= q->elevator->et->nr_requests) {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			if (!hctx->sched_tags)
+				continue;
+			sbitmap_queue_resize(&hctx->sched_tags->bitmap_tags,
+				nr - hctx->sched_tags->nr_reserved_tags);
+		}
+	} else {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			if (!hctx->sched_tags)
+				continue;
+			blk_mq_tag_update_depth(hctx, &hctx->sched_tags, nr);
 			if (ret)
 				goto out;
 		}
-- 
2.39.2