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

From: Michal Koutný
Date: Tue Aug 20 2024 - 06:01:19 EST


On Mon, Aug 19, 2024 at 11:24:18AM GMT, Tejun Heo <tj@xxxxxxxxxx> wrote:
> 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?

IIUC, bios are flushed to parent throttl group, so if there's an
ancestral limit, it should be honored. (I find this similar to memcg
reparenting.)

Mere create + set limit + delete falls under the same delegation scope,
so if that limit is bypassed, it is only self-shooting in the leg.
Shortening the lifetime of offlined structures is benefitial, no?

Michal

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