linux-kernel - Re: [PATCH v3] block: flush all throttled bios when deleting the cgroup

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Message-ID: <ZsO4ArRKhZrtDoey@slm.duckdns.org>
Date: Mon, 19 Aug 2024 11:24:18 -1000
From: Tejun Heo <tj@...nel.org>
To: Li Lingfeng <lilingfeng@...weicloud.com>
Cc: josef@...icpanda.com, hch@....de, mkoutny@...e.com, axboe@...nel.dk,
	cgroups@...r.kernel.org, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, yukuai1@...weicloud.com,
	houtao1@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com,
	yukuai3@...wei.com, lilingfeng3@...wei.com
Subject: Re: [PATCH v3] block: flush all throttled bios when deleting the
 cgroup

Hello,

On Sat, Aug 17, 2024 at 03:11:08PM +0800, Li Lingfeng wrote:
> From: Li Lingfeng <lilingfeng3@...wei.com>
> 
> When a process migrates to another cgroup and the original cgroup is deleted,
> the restrictions of throttled bios cannot be removed. If the restrictions
> are set too low, it will take a long time to complete these bios.
> 
> Refer to the process of deleting a disk to remove the restrictions and
> issue bios when deleting the cgroup.
> 
> This makes difference on the behavior of throttled bios:
> Before: the limit of the throttled bios can't be changed and the bios will
> complete under this limit;
> Now: the limit will be canceled and the throttled bios will be flushed
> immediately.

I still don't see why this behavior is better. Wouldn't this make it easy to
escape IO limits by creating cgroups, doing a bunch of IOs and then deleting
them?

Thanks.

-- 
tejun