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From: Tejun Heo <tj@kernel.org>
To: Usama Arif <usama.arif@linux.dev>
Cc: axboe@kernel.dk, cgroups@vger.kernel.org, josef@toxicpanda.com,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	shakeel.butt@linux.dev, hannes@cmpxchg.org, riel@surriel.com,
	kernel-team@meta.com
Subject: Re: [PATCH 2/3] blk-iocost: clear delay state when freeing policy data
Date: Mon, 10 Aug 2026 08:50:58 -1000	[thread overview]
Message-ID: <anodkhEpanZPbwxu@slm.duckdns.org> (raw)
In-Reply-To: <0326caea-07e7-43bf-8fe9-f2b97186e2ad@linux.dev>

> Does this unconditional call to blkcg_clear_delay() overwrite state managed
> by other policies?
> 
> Since use_delay is shared among block cgroup policies, if iocost never
> actually applied a delay, this might forcefully zero out the delay state
> managed by other active policies like blk-iolatency. 
> 
> Would it be safer to check if iocost had actually set a delay before clearing
> it here?

Yeah, this is fine. The two mechanisms aren't usually used together and even
when they step on each other, use_delay being cleared spuriously is
transient and nothing really breaks.

Thanks.

-- 
tejun

  reply	other threads:[~2026-08-10 18:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-06 18:37 [PATCH 0/3] block: skip the blkcg walk in blk_cgroup_congested() when nothing is throttled Usama Arif
2026-08-06 18:37 ` [PATCH 1/3] blk-iolatency: clear delay state when freeing policy data Usama Arif
2026-08-10 18:48   ` Tejun Heo
2026-08-06 18:37 ` [PATCH 2/3] blk-iocost: " Usama Arif
2026-08-10 16:43   ` Usama Arif
2026-08-10 18:50     ` Tejun Heo [this message]
2026-08-06 18:37 ` [PATCH 3/3] block: skip blkcg walk in blk_cgroup_congested() when nothing throttled Usama Arif
2026-08-10 18:56   ` Tejun Heo

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