linux-kernel - Re: [PATCH -next 0/4] blk-cgroup: synchronize del

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Message-ID: <Y6LiAg4u/jkrosVe@infradead.org>
Date:   Wed, 21 Dec 2022 02:37:54 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     Tejun Heo <tj@...nel.org>, 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 -next 0/4] blk-cgroup: synchronize del_gendisk() with
 configuring cgroup policy

On Tue, Dec 20, 2022 at 05:19:12PM +0800, Yu Kuai wrote:
> If we are using a mutex to protect rq_qos ops, it seems the right thing
> to do do also using the mutex to protect blkcg_policy ops, and this
> problem can be fixed because mutex can be held to alloc memroy with
> GFP_KERNEL. What do you think?

Getting rid of the atomic allocations would be awesome.

FYI, I'm also in favor of everything that moves things out of
queue_lock into more dedicated locks.  queue_lock is such an undocument
mess of untargeted things that don't realted to each other right now
that splitting and removing it is becoming more and more important.