linux-kernel - Re: [PATCH 1/3] blk-mq: remove redundant call to blk_freeze_queue_start in blk_mq_destroy

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Date:   Sat, 29 Oct 2022 17:34:49 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Jinlong Chen <nickyc975@....edu.cn>, axboe@...nel.dk,
        kbusch@...nel.org, hch@....de, sagi@...mberg.me
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org
Subject: Re: [PATCH 1/3] blk-mq: remove redundant call to
 blk_freeze_queue_start in blk_mq_destroy_queue

On 10/29/22 03:02, Jinlong Chen wrote:
> Calling blk_freeze_queue results in a redundant call to
> blk_freeze_queue_start as it has been called in blk_queue_start_drain.
> 
> Replace blk_freeze_queue with blk_mq_freeze_queue_wait to avoid the
> redundant call.

blk_mq_destroy_queue() has more callers than blk_queue_start_drain() so 
the above description is at least misleading.

Additionally, the word "cleanup" from the patch series title indicates 
that no patch in this series changes the behavior of the code. This 
patch involves a behavior change.

I think this patch introduces a hang for every caller of 
blk_mq_destroy_queue() other than blk_queue_start_drain().

Bart.