XFS log handling issue (with patch) -- (was Request for updated Ubuntu virtual kernel images)

[Kannan Manickam]

I have a Ubuntu 12.04 virtual machine with a 400 GB volume attached to it. This volume uses XFS filesystem on top of LVM2 setup and the backup system we use takes hourly backups. Since we freeze and unfreeze the filesystem during backups, I started seeing the following in the logs a lot.

Oct 14 06:52:35 localhost kernel: [4269962.940638] XFS (dm-1): xlog_space_left: head behind tail
Oct 14 06:52:35 localhost kernel: [4269962.940639] tail_cycle = 7, tail_bytes = 38953984
Oct 14 06:52:35 localhost kernel: [4269962.940640] GH cycle = 7, GH bytes = 38953976
Oct 14 06:52:35 localhost kernel: [4269962.940656] XFS (dm-1): xlog_space_left: head behind tail
Oct 14 06:52:35 localhost kernel: [4269962.940657] tail_cycle = 7, tail_bytes = 38953984
Oct 14 06:52:35 localhost kernel: [4269962.940657] GH cycle = 7, GH bytes = 38953976

This started occurred a lot and the backups were working fine for a day and then they started failing because they failed to remove the LVM snapshot using `lvremove`. After a little bit of research I found this commit in the linux kernel: https://github.com/torvalds/linux/commit/3948659e30808fbaa7673bbe89de2ae9769e20a7 which seems to fix the exact same problem I'm having.

This commit fixes this issue form kernel version 3.4 onwards. The most recent virtual kernel available for Ubuntu 12.04 LTS release is "3.2.0-49-virtual". So the possible solutions are to either backport the xfs fix to 3.2.x kernel or release virtual kernel releases for the latest version of the kernel.

I'll be happy to provide more information regarding this issue.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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