linux-kernel - [PATCH] blk-mq: quiesce queue while reallocating hctxs

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Date:   Tue, 21 Feb 2023 17:24:36 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, 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
Subject: [PATCH] blk-mq: quiesce queue while reallocating hctxs

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

commit 8237c01f1696 ("blk-mq: use quiesced elevator switch when
reinitializing queues") add quiesce queue while switching elevator,
however, if old elevator is none, queue is still not quiesced. Hence
reallocating hctxs can concurrent with run queue. Fix it by also
quiesce queue in the beginning of __blk_mq_update_nr_hw_queues().

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-mq.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d3494a796ba8..fb44ef0dff8a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4691,8 +4691,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 	if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
 		return;
 
-	list_for_each_entry(q, &set->tag_list, tag_set_list)
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
 		blk_mq_freeze_queue(q);
+		blk_mq_quiesce_queue(q);
+	}
 	/*
 	 * Switch IO scheduler to 'none', cleaning up the data associated
 	 * with the previous scheduler. We will switch back once we are done
@@ -4741,8 +4743,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 	list_for_each_entry(q, &set->tag_list, tag_set_list)
 		blk_mq_elv_switch_back(&head, q);
 
-	list_for_each_entry(q, &set->tag_list, tag_set_list)
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		blk_mq_unquiesce_queue(q);
 		blk_mq_unfreeze_queue(q);
+	}
 }
 
 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
-- 
2.31.1