From: gwendal grignou <gwendal@chromium.org>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] loop: properly observe rotational flag of underlying device
Date: Thu, 12 May 2016 20:28:34 +0000 (UTC) [thread overview]
Message-ID: <loom.20160511T213516-51@post.gmane.org> (raw)
In-Reply-To: 569438BB.6050009@googlemail.com
Holger Hoffstätte <holger.hoffstaette <at> googlemail.com> writes:
>
> On 11/11/15 23:08, Holger Hoffstätte wrote:
> > On 11/11/15 22:29, Jens Axboe wrote:
> >> On 11/11/2015 08:21 AM, Holger Hoffstätte wrote:
> >>>
> >>> The loop driver always declares the rotational flag of its device as
> >>> rotational, even when the device of the mapped file is nonrotational,
> >>> as is the case with SSDs or on tmpfs. This can confuse filesystem
tools
> >>> which are SSD-aware; in my case I frequently forget to tell
mkfs.btrfs
> >>> that my loop device on tmpfs is nonrotational, and that I really
don't
> >>> need any automatic metadata redundancy.
> >>>
> >>> The attached patch fixes this by introspecting the rotational flag of
the
> >>> mapped file's underlying block device, if it exists. If the mapped
file's
> >>> filesystem has no associated block device - as is the case on e.g.
tmpfs -
> >>> we assume nonrotational storage. If there is a better way to identify
such
> >>> non-devices I'd love to hear them.
> >>>
> >>> Signed-off-by: Holger Hoffstätte <holger.hoffstaette <at>
googlemail.com>
>
> Jens,
>
> I haven't seen this merged in any trees yet and was wondering if there's
> any chance to get this into 4.5? If there's something left to fix up
please
> let me know.
>
> Thanks,
> Holger
>
>
This patch proved useful for ureadahead: when we use it on a loop device,
it would use the HDD method to place the data in cache using the pack
information instead of the SSD method.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
next prev parent reply other threads:[~2016-05-12 20:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-11 15:21 [PATCH] loop: properly observe rotational flag of underlying device Holger Hoffstätte
2015-11-11 21:29 ` Jens Axboe
2015-11-11 22:08 ` Holger Hoffstätte
2016-01-11 23:20 ` Holger Hoffstätte
2016-05-12 20:28 ` gwendal grignou [this message]
2016-05-12 22:30 ` Holger Hoffstätte
2019-02-12 22:54 Benjamin Gordon
2019-03-26 16:55 ` Holger Hoffstätte
[not found] ` <CADaYBq32aM4QpHmOmevFWSkjYqWmBWdhgd7CDWh+Se6q_2byHg@mail.gmail.com>
2019-03-26 17:57 ` Jens Axboe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=loom.20160511T213516-51@post.gmane.org \
--to=gwendal@chromium.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.