BTRFS is completly unusable on 15.10

[QkiZ]

btrfs can see subvolumes but can't manipulate them. For example I can list subvolumes:

sudo btrsfs subvol list /
ID 385 gen 77889 top level 5 path @
ID 416 gen 77410 top level 5 path @apt-snapshot-release-upgrade-wily-2015-10-23_23:25:25
ID 417 gen 77742 top level 5 path @apt-snapshot-2015-10-23_23:25:26
ID 418 gen 77412 top level 417 path @apt-snapshot-2015-10-23_23:25:26/@
ID 419 gen 77413 top level 5 path @apt-snapshot-2015-10-23_23:25:27

But I cant delete them:

sudo btrfs subvol delete /@apt-snapshot-release-upgrade-wily-2015-10-23_23:25:25
ERROR: error accessing '/@apt-snapshot-release-upgrade-wily-2015-10-23_23:25:25'

Even if I mount rootfs in another mountpoint:

sudo mount /dev/mapper/system-root /mnt/
sudo btrfs subvol delete /mnt/@apt-snapshot-release-upgrade-wily-2015-10-23_23:25:25
ERROR: error accessing '/mnt/@apt-snapshot-release-upgrade-wily-2015-10-23_23:25:25'

I can't see subvolumes in root directory, I see files in subvolumes.

ls /mnt/
bin dev initrd.img lib32 mnt root srv usr vmlinuz.old
boot etc initrd.img.old lib64 opt run sys var
core home lib

When I'm boot live Ubuntu 15.04 from CD I can manipulate subvolumes with no problems.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: btrfs-tools 4.0-2
ProcVersionSignature: Ubuntu 4.2.0-17.20-lowlatency 4.2.3
Uname: Linux 4.2.0-17-lowlatency x86_64
ApportVersion: 2.19.1-0ubuntu3
Architecture: amd64
Date: Sat Oct 24 14:25:58 2015
InstallationDate: Installed on 2015-02-13 (252 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Release amd64 (20141022.1)
SourcePackage: btrfs-tools
UpgradeStatus: Upgraded to wily on 2015-10-23 (0 days ago)

[Alexander Fougner (fougner)]

Hi,

Is it possible that you've set the default subvolume to something else than the actual filesystem root? You can check this by doing the following.

$ sudo btrfs subvol get-default <mountpoint>

Also, after you try to mount the root in /mnt, could you please post the output of the relevant parts of /proc/mounts ?

[QkiZ (qkiz)]

In this version of Ubuntu BTRFS change mount method. If you mount BTRFS volume without any options it mounts in default subvol, not in root. If I want to get root of volume or any other subvolume I must use subvol mount option.