linux-kernel - Re: [PATCH -next 3/5] blk-iocost: prevent configuration update concurrent with io throttling

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Message-ID: <Y0Wh0fQBkKlhEiYi@slm.duckdns.org>
Date:   Tue, 11 Oct 2022 07:03:13 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com
Subject: Re: [PATCH -next 3/5] blk-iocost: prevent configuration update
 concurrent with io throttling

On Tue, Oct 11, 2022 at 04:35:45PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> This won't cause any severe problem currently, however, this doesn't
> seems appropriate:
> 
> 1) 'ioc->params' is read from multiple places without holding
> 'ioc->lock', unexpected value might be read if writing it concurrently.
> 
> 2) If configuration is changed while io is throttling, the functionality
> might be affected. For example, if module params is updated and cost
> becomes smaller, waiting for timer that is caculated under old
> configuration is not appropriate.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun