linux-btrfs.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Liu Bo <liub.liubo@gmail.com>
To: Florian Lindner <mailinglists@xgm.de>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: subvolumes: default and IDs
Date: Mon, 30 Jul 2012 20:18:16 +0800	[thread overview]
Message-ID: <50167B88.3080500@gmail.com> (raw)
In-Reply-To: <CAJtBfr-ndERMvhG2dEwKJVsUe++sqGk_ZU=0gHDr3vbZLSyo_w@mail.gmail.com>

On 07/30/2012 03:56 PM, Florian Lindner wrote:
> Hey!
>
> I recently starting playing with btrfs and subvolume, but it has left
> me puzzled:
> Distribution is Archlinux, Kernel is 3.4.6.
>
>>>>
> root@horus /mnt # mkfs.btrfs -L test /dev/sdb1
>
> WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> fs created label test on /dev/sdb1
>          nodesize 4096 leafsize 4096 sectorsize 4096 size 2.73TB
> Btrfs Btrfs v0.19
> root@horus /mnt # mount /dev/sdb1 test
> root@horus /mnt # cd test
> root@horus /mnt/test # btrfs subvolume create sv1
> Create subvolume './sv1'
> root@horus /mnt/test # btrfs subvolume create sv2
> Create subvolume './sv2'
> root@horus /mnt/test # touch sv1/sv1.file
> root@horus /mnt/test # touch sv2/sv2.file
> root@horus /mnt/test # btrfs subvolume get-default .
> ID 256 top level 5 path sv1
> ID 259 top level 5 path sv2
> <<<
>
> What is the default subvolume now? How can I tell?
>
>>>>
> root@horus /mnt/test # btrfs subvolume set-default 259 .
> root@horus /mnt/test # btrfs subvolume get-default .
> ID 256 top level 5 path sv1
> ID 259 top level 5 path sv2
> <<<
>
> Seems to have changed nothing....?
>
>>>>
> root@horus /mnt/test # cd ..
> root@horus /mnt # umount test && mount /dev/sdb1 test
> root@horus /mnt # ls test
> sv2.file
> <<<
>
> Ah, sv2 seems to be default, like I had set it.
>
>>>>
> root@horus /mnt # btrfs subvolume set-default 5 test
> root@horus /mnt # umount test && /mnt # mount /dev/sdb1 test
> root@horus /mnt # ls test
> sv1/  sv2/
> <<<
>
> Ok, 5 seems to be the root subvolume id. Is it always like that? I
> remembered to have read somewhere it was 0 ? (which makes a kind of
> more sense for me)
>
>>>>
> root@horus /mnt # btrfs subvolume set-default 256 test
> root@horus /mnt # umount test && mount /dev/sdb1 test
> root@horus /mnt # ls test
> sv1.file
> <<<
>
> Fine! But:
>
>>>>
> root@horus /mnt # btrfs subvolume set-default 0 test
> root@horus /mnt # umount test && mount /dev/sdb1 test
> root@horus /mnt # ls test
> sv1.file
> <<<
>
> set-default 0 seems to do nothing but does not produce an error
> either. What about subvolume 0? Still I can do:
>
>>>>
> root@horus /mnt # umount test
> root@horus /mnt # mount -o subvolid=0 /dev/sdb1 test
> root@horus /mnt # ls test
> sv1/  sv2/
> <<<
>
> Ok, here 0 as subvolid works. What about subvolid=5?
>
>>>>
> root@horus /mnt # umount test
> root@horus /mnt # mount -o subvolid=5 /dev/sdb1 test
> root@horus /mnt # ls test
> sv1/  sv2/
> <<<
>
> Works too.
>
> Sorry for the lengthy posting, but writing this posting has puzzled me
> even more I was yesterday. I hope someone could shed some light on it.
>

Hi Florian,

Thanks for reporting these!

They are old bugs that had been fixed recently in latest btrfs progs,
you can checkout the latest btrfs-progs from
git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs.git

subvolid=0 will be translated to subvolid=5 since 5 indicates btrfs' fs 
tree (the root subvolume as you mentioned)

thanks,
liubo

> Thanks!
>
> Florian
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>


  parent reply	other threads:[~2012-07-30 12:18 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-30  7:56 subvolumes: default and IDs Florian Lindner
2012-07-30 11:29 ` Calvin Walton
2012-07-30 12:43   ` Swâmi Petaramesh
2012-07-30 12:18 ` Liu Bo [this message]
2012-07-31  0:28 ` Alexander Karbstein
2012-07-31  0:50 ` Alexander Karbstein
2012-07-31  0:53   ` [PATCH] Btrfs-progs: Enabled setting root subvolume with subvolid=0 Alexander Karbstein
2012-07-31  1:26     ` Liu Bo
2012-07-31  2:09       ` Alexander Karbstein
2012-07-31 17:11       ` [PATCH V2] " Alexander Karbstein
2012-07-31 17:11       ` Alexander Karbstein

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=50167B88.3080500@gmail.com \
    --to=liub.liubo@gmail.com \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=mailinglists@xgm.de \
    /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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).