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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
Subject: Re: [PATCH v2 1/2] blk-iocost: add refcounting for iocg
Date: Wed, 4 Jan 2023 11:44:49 -1000	[thread overview]
Message-ID: <Y7XzUee5Bq+DoIC1@slm.duckdns.org> (raw)
In-Reply-To: <20221227125502.541931-2-yukuai1@huaweicloud.com>

On Tue, Dec 27, 2022 at 08:55:01PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> iocost requires that child iocg must exit before parent iocg, otherwise
> kernel might crash in ioc_timer_fn(). However, currently iocg is exited
> in pd_free_fn(), which can't guarantee such order:
> 
> 1) remove cgroup can concurrent with deactivate policy;
> 2) blkg_free() triggered by remove cgroup is asynchronously, remove
> child cgroup can concurrent with remove parent cgroup;
> 
> Fix the problem by add refcounting for iocg, and child iocg will grab
> reference of parent iocg, so that parent iocg will wait for all child
> iocg to be exited.

Wouldn't it be better to do this refcnting in the blk-cgroup core code
rather than in blk-iocost?

Thanks.

-- 
tejun

  reply	other threads:[~2023-01-04 21:46 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-27 12:55 [PATCH v2 0/2] blk-iocost: add refcounting for iocg and ioc Yu Kuai
2022-12-27 12:55 ` [PATCH v2 1/2] blk-iocost: add refcounting for iocg Yu Kuai
2023-01-04 21:44   ` Tejun Heo [this message]
2023-01-05  1:14     ` Yu Kuai
2023-01-05 18:32       ` Tejun Heo
2023-01-06  1:08         ` Yu Kuai
2023-01-06 20:18           ` Tejun Heo
2023-01-09  1:32             ` Yu Kuai
2023-01-09 18:23               ` Tejun Heo
2023-01-10  1:39                 ` Yu Kuai
2023-01-10 18:36                   ` Tejun Heo
2023-01-11  1:36                     ` Yu Kuai
2023-01-11 17:07                       ` Tejun Heo
2023-01-12  6:18                         ` Yu Kuai
2023-01-13  0:53                           ` Tejun Heo
2023-01-13  1:10                             ` Yu Kuai
2023-01-13  1:15                               ` Tejun Heo
2023-01-13  1:25                                 ` Yu Kuai
2023-01-13 17:16                                   ` Tejun Heo
2023-01-16  3:25                                     ` Yu Kuai
2022-12-27 12:55 ` [PATCH v2 2/2] blk-iocost: add refcounting for ioc Yu Kuai
2023-01-04 21:45   ` Tejun Heo

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