linux-kernel - Re: [PATCH v4 1/1] loop: scale loop device by introducing per device lock

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Message-ID: <daf21294-f51e-3f03-8a46-d0181104d9e3@kernel.dk>
Date:   Tue, 26 Jan 2021 13:09:05 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Tatashin <pasha.tatashin@...een.com>,
        tyhicks@...ux.microsoft.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, sashal@...nel.org, jmorris@...ei.org,
        lukas.bulwahn@...il.com, hch@....de, pvorel@...e.cz,
        ming.lei@...hat.com, mzxreary@...inter.de, mcgrof@...nel.org,
        zhengbin13@...wei.com, maco@...roid.com, colin.king@...onical.com,
        evgreen@...omium.org
Subject: Re: [PATCH v4 1/1] loop: scale loop device by introducing per device
 lock

On 1/26/21 7:46 AM, Pavel Tatashin wrote:
> Currently, loop device has only one global lock: loop_ctl_mutex.
> 
> This becomes hot in scenarios where many loop devices are used.
> 
> Scale it by introducing per-device lock: lo_mutex that protects
> modifications of all fields in struct loop_device.
> 
> Keep loop_ctl_mutex to protect global data: loop_index_idr, loop_lookup,
> loop_add.
> 
> The new lock ordering requirement is that loop_ctl_mutex must be taken
> before lo_mutex.

Applied, thanks.

-- 
Jens Axboe