missing space on btrfs partition

[ill]

df -h shows on a 9.8GB partition that only 6.4GB are used, but at the same time the amount available is shown to be 15MB, with a usage percent of 100.
---
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: luke 1590 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xfe9fc000 irq 47'
   Mixer name : 'SigmaTel STAC9228'
   Components : 'HDA:14f12c06,14f1000f,00100000 HDA:10951392,1028022f,00100000 HDA:83847616,1028022f,00100402'
   Controls : 22
   Simple ctrls : 12
DistroRelease: Ubuntu 11.10
InstallationMedia: Kubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
MachineType: Dell Inc. Inspiron 1525
Package: linux (not installed)
ProcEnviron:
 LANGUAGE=
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-3.0.0-12-generic root=UUID=7502179e-dcf0-4055-bd7c-0c0304e3cb6b ro rootflags=subvol=@ elevator=deadline quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
RelatedPackageVersions:
 linux-restricted-modules-3.0.0-12-generic N/A
 linux-backports-modules-3.0.0-12-generic N/A
 linux-firmware 1.60
Tags: oneiric
Uname: Linux 3.0.0-12-generic x86_64
UpgradeStatus: Upgraded to oneiric on 2011-10-14 (2 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
dmi.bios.date: 10/27/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A17
dmi.board.name: 0U990C
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA17:bd10/27/2009:svnDellInc.:pnInspiron1525:pvr:rvnDellInc.:rn0U990C:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Inspiron 1525
dmi.sys.vendor: Dell Inc.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 874684

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[ill (illumilore)]

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[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? It will allow additional upstream developers to examine the issue. Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the release candidate kernel versus the daily build. Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text. Please let us know your results.

Thanks in advance.

[Rolf Leggewie (r0lf)]

I have the same issue in a freshly installed precise system. The ratio of lost space is similar for me as well.

From "df -h"
/dev/mapper/X20VG-PRECISE_VAR 488M 140M 168M 46% /var

[Rolf Leggewie (r0lf)]

This is still the same in today's mainline kernel.

[Joseph Salisbury (jsalisbury)]

This issue appears to be an upstream bug, since you tested the latest upstream kernel. Would it be possible for you to open an upstream bug report at bugzilla.kernel.org? That will allow the upstream Developers to examine the issue, and may provide a quicker resolution to the bug.

If you are comfortable with opening a bug upstream, It would be great if you can report back the upstream bug number in this bug report. That will allow us to link this bug to the upstream report.

[Rolf Leggewie (r0lf)]

Joseph, I would have happily opened an upstream ticket but I think upstream bugzilla is offline for the moment. I suppose that's due to the recent break-in?

[Joseph Salisbury (jsalisbury)]

Yes, it appears that bugzilla.kernel.org is still unavailable. One alternative would be to report this directly to the subsystem maintainer or to the LKML.

[ill (illumilore)]

What is the contact information for the subsystem maintainer or LKML?

[Rolf Leggewie (r0lf)]

There are many reports upstream about similar problems, some of them fairly old :-(

https://bugzilla.kernel.org/show_bug.cgi?id=14779
https://bugzilla.kernel.org/show_bug.cgi?id=12555
https://bugzilla.kernel.org/show_bug.cgi?id=14113
https://bugzilla.kernel.org/show_bug.cgi?id=16066

[Rolf Leggewie (r0lf)]

upstream tickets have all since been closed as obsolete. Is this still a problem for anyone?

[Rolf Leggewie (r0lf)]

I've never really dared to use btrfs since back in 2012 it was still horribly broken and I value my files. From what I can see, the problem discussed in this ticket is fixed in the version in trusty.

[Michael Murphy (mmstick)]

This shouldn't be a problem, but if you realize that btrfs is using more space than it should be, defragmenting and rebalancing will recover it. For example: sudo btrfs filesystem defragment /; sudo btrfs filesystem balance /

[Rolf Leggewie (r0lf)]

I will mark the Ubuntu task as fix released. Please feel free to reopen (with appropriate information) if you still experience this.