-------- Original Message --------
Subject: Re: btrfs and mount in gentoo linux
From: Stefan G. Weichinger <li...@xunil.at>
To: linux-btrfs@vger.kernel.org
Date: 2014年07月09日 04:52
Am 08.07.2014 22:19, schrieb Holger Hoffstätte:
On Tue, 08 Jul 2014 21:07:30 +0200, Stefan G. Weichinger wrote:
I am a happy btrfs-user with gentoo linux for some time now and noticed
that the command "mount" does not show me which subvolid is mounted where.
Interestingly I just found that this came up in Fedora some time ago:
https://bugzilla.redhat.com/show_bug.cgi?id=743118
findmnt seems to do the trick, so the underlying functionality in
libmnt seems to work. Maybe Debian's mount does something differently?
findmnt does not fully show the subvolids or names:
# findmnt | grep btrfs
/ /dev/sda3[/rootfs] btrfs
rw,noatime,compress=lzo,ssd,space_cache
├─/mnt/uncow /dev/sda3 btrfs
rw,noatime,compress=lzo,ssd,space_cache
└─/home/sgw /dev/mapper/_dev_sda4 btrfs
rw,noatime,compress=lzo,ssd,space_cache
The "[/rootfs]" is something in the right direction ...
The bug is that, if you don't use 'subvol=' mount option but use default
subvolume or 'subvolid=' mount option,
findmnt will not give the output.
Since 'subvol=' mount option differs from default subvolume mount or
'subvolid=' mount option in calling behavior,
'subvol=' uses mount_subtree() vfs call, which records subtree mount info.
On the other hand, default subvolume mount or 'subvolid=' mount does not
go through the vfs subtree mount
but use btrfs's implement, which does not report vfs submount.
I'll try to investigate further and find whether we can fix it to show
more info.
Thanks,
Qu
S
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