linux-kernel - Re: [PATCH] blk-cgroup: fix missing pd_online

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Message-ID: <20230105104241.GA16920@blackbody.suse.cz>
Date:   Thu, 5 Jan 2023 11:45:08 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     tj@...nel.org, josef@...icpanda.com, axboe@...nel.dk,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] blk-cgroup: fix missing pd_online_fn() while activating
 policy

On Thu, Jan 05, 2023 at 09:43:02AM +0800, Yu Kuai <yukuai1@...weicloud.com> wrote:
> This is based only on code review, currently the only negative effects
> is that root blkg from blk-throtl won't call pd_online_fn().

Good, that's a NOP and there are no other uses of pd_online_fn.

I wonder are the separate pd_init_fn and pd_online_fn callbacks
necessary today?
(IOW your fixup is a good catch and looks correct to me; I'd suggest
more of a clean up. Shall I look into that?)

> No, this is not true, before blkcg_activate_policy() is called,
> blkg_create() won't see this policy, hence pd_init_fn/pd_online_fn won't
> be called from blkg_create().

Thanks, I missed the q->blkcg_pols bit.

Michal

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