linux-kernel - Re: [PATCH v2 1/2] blk-iocost: add refcounting for iocg

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Message-ID: <Y8CwwghZ0adMsHFC@slm.duckdns.org>
Date:   Thu, 12 Jan 2023 15:15:46 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     hch@...radead.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,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2 1/2] blk-iocost: add refcounting for iocg

Hello,

On Fri, Jan 13, 2023 at 09:10:25AM +0800, Yu Kuai wrote:
> > only activate the policy when the controller is actually enabled. So, idk.
> > What's wrong with synchronizing the two removal paths? blkcg policies are
> > combinations of cgroups and block device configurations, so having exit
> > paths from both sides is kinda natural.
> 
> I still can't figure out how to synchronizing them will a mutex. Maybe
> I'm being foolish...

Hmm... can't you just use e.g. per-bdev mutex which is grabbed by both
blkg_free_workfn() and blkcg_deactivate_policy()?

Thanks.

-- 
tejun