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Message-ID: <2edc9a06c00cc96958723d0e09803104@kernel.org>
From: Tejun Heo <tj@kernel.org>
To: Peng Yu <yupeng0921@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	=?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>,
	Josef Bacik <josef@toxicpanda.com>, Jens Axboe <axboe@kernel.dk>,
	Maurizio Lombardi <mlombard@arkamax.eu>, cgroups@vger.kernel.org,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/2] cgroup: export cgroup_e_css()
In-Reply-To: <20260926063328.257023-2-yupeng0921@gmail.com>
References: <20260926063328.257023-1-yupeng0921@gmail.com>
 <20260926063328.257023-2-yupeng0921@gmail.com>
Date: Sat, 26 Sep 2026 07:38:12 -1000
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Hello, Peng.

On Fri, Sep 25, 2026 at 11:33:27PM -0700, Peng Yu wrote:
> The nvmet invokes the cgroup_e_css for each bio and under
> the rcu protection.

cgroup_e_css() walks up the hierarchy to find the effective css, and I
don't think we want to do that on every IO. Can you update cgroup core to
track the effective css in each cgroup and make cgroup_e_css() use that
instead?

Thanks.

-- 
tejun