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

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Message-ID: <lke5obdxztncs2mtbvgylngxspzzzrmlveibye32cqwog7xw5a@bk22ajawnbtn>
Date: Thu, 27 Jun 2024 16:48:42 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Li Lingfeng <lilingfeng@...weicloud.com>
Cc: tj@...nel.org, josef@...icpanda.com, hch@....de, axboe@...nel.dk, 
	cgroups@...r.kernel.org, linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	yangerkun@...wei.com, yukuai1@...weicloud.com, houtao1@...wei.com, yi.zhang@...wei.com, 
	lilingfeng3@...wei.com
Subject: Re: [PATCH] block: cancel all throttled bios when deleting the cgroup

On Tue, Jun 25, 2024 at 07:38:34PM GMT, Li Lingfeng <lilingfeng@...weicloud.com> wrote:
> Thanks for your advice. It's indeed more appropriate to use "flush" instead
> of "cancel" here, I will change it soon.

I saw your v2. Didn't you forget to change also the function name?

> I didn't quite get what you mean. Do you mean this patch will cause a change
> in mechanics, and it is necessary to add an explanation?
> 
> (After deleting the original cgroup,
>  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 mean -- can the new mechanics be exploited to bypass throttling by
sending IO from a process, migrate it between cgroups and rmdir them?
That should be covered in the commit log.

Thanks,
Michal

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