[SOLVED] Aufs mounts "crashing" on unmount

falconindy · 2010-01-10 05:58:45

I'm writing the above backup script that employs Aufs and SquashFS to attain compression as well as daily incremental backups. The general gist of it is that I have a directory for each incremental (day), and its overlayed on top of a squashfs compressed seed using Aufs to present the most up to date backup. Depending on how many of these bins you mount and the order you mount them in, I'm controlling which bin is written to, or intentionally not mounting a bin in the case of a rollback.

The problem I'm running into is that the aufs mount is (often, but not always) hanging when i dismount it. I sometimes can't SIGINT the process, and any other process that tries to touch that entire drive results in it going straight to disk sleep. During this time, /proc/mounts will report that the union has been unmounted, but the corresponding entry is not removed from /etc/mtab. Disk, CPU and RAM usage are all at idle. Given enough time (10-15 minutes), the system will return to normal. There is nothing relevant in /var/log/everything.log. If I try to mount another Aufs mount while the previous one is hanging, the new mount will hang in similar fashion.

I did this originally on a btrfs formatted drive, and tried it again tonight on ext4 with the same hangup. I've also tried allowing some wait time in between operations of the script, thinking that the mount needed time to sync before I could cleanly unmount it. Along similar lines, I tried voluntarily calling "auplink <mount> flush" before unmounting. No joy there either.

I know there was some changes to Aufs in 2.6.32, could this be related?

I'm happy to provide anything else if requested, but I'm afraid this is the best I can come up with right now as there's nothing in the logs to report.

Last edited by falconindy (2010-01-11 20:59:51)

mikesd · 2010-01-10 06:56:18

I don't use aufs however I did see it mentioned on the mailing list[1] recently. Might be worth checking out.

[1] http://mailman.archlinux.org/pipermail/ … 14847.html

falconindy · 2010-01-10 17:56:55

I guess I should have mentioned that I roll my own kernel...

Name           : kernel26-ckzero
Version        : 2.6.32.3-1
Build Date     : Fri 08 Jan 2010 11:15:55 AM EST
Install Date   : Fri 08 Jan 2010 11:16:26 AM EST

Name           : aufs2-ckzero
Version        : 2.6.32_20091203-1
Build Date     : Fri 08 Jan 2010 11:18:16 AM EST
Install Date   : Fri 08 Jan 2010 11:18:16 AM EST

edit: I was lucky enough to stumble on a great candidate for a headless server last night so I'll be testing there as well on a vanilla (64-bit) kernel. (update: same hanging there as well)

Last edited by falconindy (2010-01-10 19:15:32)

falconindy · 2010-01-11 20:59:40

Looks like I'm a victim of this flyspray entry. Mounting an ext4 partition with the 'nobarrier' option seems to help. Still no resolution for btrfs, though.

Arch Linux

#1 2010-01-10 05:58:45

[SOLVED] Aufs mounts "crashing" on unmount

#2 2010-01-10 06:56:18

Re: [SOLVED] Aufs mounts "crashing" on unmount

#3 2010-01-10 17:56:55

Re: [SOLVED] Aufs mounts "crashing" on unmount

#4 2010-01-11 20:59:40

Re: [SOLVED] Aufs mounts "crashing" on unmount

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