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From: Tejun Heo <tj@kernel.org>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk,
	cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, yukuai3@huawei.com,
	yi.zhang@huawei.com, yangerkun@huawei.com
Subject: Re: [PATCH -next 3/4] block/rq_qos: use a global mutex to protect rq_qos apis
Date: Wed, 4 Jan 2023 11:39:47 -1000	[thread overview]
Message-ID: <Y7XyIzGptuqO8EAt@slm.duckdns.org> (raw)
In-Reply-To: <20230104085354.2343590-4-yukuai1@huaweicloud.com>

On Wed, Jan 04, 2023 at 04:53:53PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> This patch fix following problems:
> 
> 1) rq_qos_add() and rq_qos_del() is protected, while rq_qos_exit() is
>    not.

This part makes sense.

> 2) rq_qos_add() and blkcg_activate_policy() is not atomic, if
>    rq_qos_exit() is done before blkcg_activate_policy(),
>    null-ptr-deference can be triggered.

I'm not sure this part does. I think it'd be better to guarantee that device
destruction is blocked while these configuration operations are in progress
which can be built into blkg_conf helpers.

Thanks.

-- 
tejun

  reply	other threads:[~2023-01-04 21:39 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-04  8:53 [PATCH -next 0/4] block/rq_qos: protect rq_qos apis with global mutex Yu Kuai
2023-01-04  8:53 ` [PATCH -next 1/4] block/rq_qos: move implementions of init/exit rq-qos apis to blk-rq-qos.c Yu Kuai
2023-01-04 21:30   ` Tejun Heo
2023-01-04  8:53 ` [PATCH -next 2/4] block/rq_qos: factor out a helper to add rq_qos and activate policy Yu Kuai
2023-01-04  8:53 ` [PATCH -next 3/4] block/rq_qos: use a global mutex to protect rq_qos apis Yu Kuai
2023-01-04 21:39   ` Tejun Heo [this message]
2023-01-05  0:28     ` Tejun Heo
2023-01-05  1:35       ` Yu Kuai
2023-01-05 18:34         ` Tejun Heo
2023-01-06  1:33           ` Yu Kuai
2023-01-06 18:23             ` Tejun Heo
2023-01-09  1:38               ` Yu Kuai
2023-01-09  6:37                 ` Yu Kuai
2023-01-04  8:53 ` [PATCH -next 4/4] block/rq_qos: fail rq_qos_add() after rq_qos_exit() Yu Kuai

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