linux-kernel - Re: [PATCH v3 1/1] loop: scale loop device by introducing per device lock

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Message-ID: <YA/fwFU+Wg6+jr85@pevik>
Date:   Tue, 26 Jan 2021 10:24:16 +0100
From:   Petr Vorel <pvorel@...e.cz>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     tyhicks@...ux.microsoft.com, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        sashal@...nel.org, jmorris@...ei.org, lukas.bulwahn@...il.com,
        hch@....de, 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 v3 1/1] loop: scale loop device by introducing per device
 lock

Hi,

> 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 the
> fields in struct loop_device. Keep loop_ctl_mutex to protect global
> data such as loop_index_idr, loop_lookup, loop_add.

> Lock ordering: loop_ctl_mutex > lo_mutex.

Reviewed-by: Petr Vorel <pvorel@...e.cz>

Kind regards,
Petr