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From:   Martijn Coenen <maco@android.com>
Date:   Thu, 15 Aug 2019 15:49:58 +0100
Message-ID: <CAB0TPYGczqoDz=ReM75cYc4hbS58V-a4m_qJ8GoAoWtepXTWNA@mail.gmail.com>
Subject: Re: [PATCH] RFC: loop: Avoid calling blk_mq_freeze_queue() when possible.
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     axboe@kernel.dk, linux-block@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>, kernel-team@android.com,
        Narayan Kamath <narayan@google.com>,
        Dario Freni <dariofreni@google.com>,
        Nikita Ioffe <ioffe@google.com>,
        Jiyong Park <jiyong@google.com>,
        Martijn Coenen <maco@google.com>
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On Wed, Aug 14, 2019 at 4:29 PM Bart Van Assche <bvanassche@acm.org> wrote:
> Hi Martijn,
>
> Is the loop driver used in Android Q to make a file on a filesystem
> visible as a block device or rather to make a subset of a block device
> visible as a block device? In the latter case, have you considered to
> use the dm-linear driver instead? I expect that the overhead per I/O of
> dm-linear will be lower than that of the loop driver.

Hi Bart,

In this case we're using the loop driver to make a file on the
filesystem visible as a block device (in the file is a filesystem we
want to mount), so unfortunately dm-linear is not an option.

Best,
Martijn

>
> Bart.