Identify mounted subvolume

Identify mounted subvolume

[Juan Orti Alcaine]

I cannot find the answer to this one. How can I determine which 
subvolume I have mounted in a certain path? I'm looking through /sys but 
no clue.

Thank you.

-- 
Juan Orti
https://miceliux.com

Re: Identify mounted subvolume

[Hugo Mills]

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On Tue, Oct 07, 2014 at 10:47:56AM +0200, Juan Orti Alcaine wrote:
> I cannot find the answer to this one. How can I determine which subvolume I
> have mounted in a certain path? I'm looking through /sys but no clue.

   Rumour has it that /proc/self/mountinfo is meant to have the
information, but I've just checked, and it doesn't seem to have the
subvol in it on my server (3.16.2).

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
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Re: Identify mounted subvolume

[Qu Wenruo]

-------- Original Message --------
Subject: Re: Identify mounted subvolume
From: Hugo Mills <hugo@carfax.org.uk>
To: Juan Orti Alcaine <juan.orti@miceliux.com>
Date: 2014年10月07日 17:06
> On Tue, Oct 07, 2014 at 10:47:56AM +0200, Juan Orti Alcaine wrote:
>> I cannot find the answer to this one. How can I determine which subvolume I
>> have mounted in a certain path? I'm looking through /sys but no clue.
>     Rumour has it that /proc/self/mountinfo is meant to have the
> information, but I've just checked, and it doesn't seem to have the
> subvol in it on my server (3.16.2).
>
>     Hugo.
>
This accepted patch will make /proc/self/mountinfo to have all the info.
https://patchwork.kernel.org/patch/4593831/

But I didn't see it in 3.17 kernel or integration branch, maybe next 
merge window?

Even without the patch, when mounting using '-o subvol=' mount option 
will also fill the /proc/self/mountinfo,
using 3.16.4.
---
149 19 0:39 / /mnt/btrfs rw,relatime shared:101 - btrfs /dev/sda6 
rw,space_cache
153 19 0:39 */subvol1* /mnt/other rw,relatime shared:104 - btrfs 
/dev/sda6 rw,space_cache
---

On the other hand, without the patch and you mount with '-o subvolid=', 
then mountinfo will not help.

Thanks,
Qu

Re: Identify mounted subvolume

[Hugo Mills]

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On Tue, Oct 07, 2014 at 05:18:51PM +0800, Qu Wenruo wrote:
> 
> -------- Original Message --------
> Subject: Re: Identify mounted subvolume
> From: Hugo Mills <hugo@carfax.org.uk>
> To: Juan Orti Alcaine <juan.orti@miceliux.com>
> Date: 2014年10月07日 17:06
> >On Tue, Oct 07, 2014 at 10:47:56AM +0200, Juan Orti Alcaine wrote:
> >>I cannot find the answer to this one. How can I determine which subvolume I
> >>have mounted in a certain path? I'm looking through /sys but no clue.
> >    Rumour has it that /proc/self/mountinfo is meant to have the
> >information, but I've just checked, and it doesn't seem to have the
> >subvol in it on my server (3.16.2).
> >
> >    Hugo.
> >
> This accepted patch will make /proc/self/mountinfo to have all the info.
> https://patchwork.kernel.org/patch/4593831/
> 
> But I didn't see it in 3.17 kernel or integration branch, maybe next merge
> window?
> 
> Even without the patch, when mounting using '-o subvol=' mount option will
> also fill the /proc/self/mountinfo,
> using 3.16.4.
> ---
> 149 19 0:39 / /mnt/btrfs rw,relatime shared:101 - btrfs /dev/sda6
> rw,space_cache
> 153 19 0:39 */subvol1* /mnt/other rw,relatime shared:104 - btrfs /dev/sda6
> rw,space_cache
> ---

   Aaaah, I see. I was just misinterpreting the information.

> On the other hand, without the patch and you mount with '-o subvolid=', then
> mountinfo will not help.

   Got it. Thanks for clearing up my lack of understanding.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
         --- Unix:  For controlling fungal diseases in crops ---         

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