linux-kernel - Re: [PATCH v3 -next 1/2] blk-cgroup: don't call blk_mq_freeze_queue() in blkcg_deactivate

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Message-ID: <YW75wUcf9CcmqdD5@slm.duckdns.org>
Date:   Tue, 19 Oct 2021 07:00:49 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     axboe@...nel.dk, paolo.valente@...aro.org,
        avanzini.arianna@...il.com, fchecconi@...il.com,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH v3 -next 1/2] blk-cgroup: don't call
 blk_mq_freeze_queue() in blkcg_deactivate_policy()

Hello,

On Tue, Oct 19, 2021 at 10:41:31AM +0800, Yu Kuai wrote:
> blkcg_deactivate_policy() can be called from either
> blk_cleanup_queue() for all policies or elevator_switch() for bfq
> policy. Thus there is no need to freeze queue in
> blkcg_deactivate_policy() since the caller freeze the queue aready.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

I would just keep the calls. The operation requires the q to be frozen and
there isn't a good way to annotate that the caller must be holding a usage
count, so it's useful even just as documentation.

Thanks.

-- 
tejun