[RESEND] btrfs corruption / cannot mount

[RESEND] btrfs corruption / cannot mount

[Riccardo Berto]

Hi
I'm a btrfs user since I encountered the ext4 3.6.2 bug and then I
decided to switch.

Today I was using my system when the /home btrfs filesystem get
corrupted. I rebooted almost instantly but it couldn't mount /home
(/dev/sda4). So I disabled the /home automount in fstab in order to
have gnome working again and I logged in to freenode on #btrfs channel
for having support.
I met "darksatanic" who gave me suggestions to have /home mounted again.
I tried with him to mount /home manually with -o recovery (it didn't
worked). Then I did btrfs-zero-log /dev/sda4 and then it mounted, but
only a time. There were no files in there: only the dirs mountpoints
to my external HD. So I launched btrfs-restore /dev/sda4 /mnt/ and it
restored only some dotfiles (not all).
He then took me to write to mailing list attaching my logs, hoping for
someone with more clue who can help me.

Now it seems to work fine, I will stick with this fs until your needs
in order to give you logs to better understand what happened.


dmesg containing my try with "recovery" mountflag -->
http://pastebin.com/x1rDsfHu

btrfs-find-root /dev/sda4 log -->http://pastebin.com/WHbDC2xq


--
Linux Registered User (http://linuxcounter.net) #550720

Re: [RESEND] btrfs corruption / cannot mount

[Michael Kjörling]

On 2 Dec 2012 09:49 +0100, from riccardobrt@gmail.com (Riccardo Berto):
> I'm a btrfs user since I encountered the ext4 3.6.2 bug and then I
> decided to switch.

> Now it seems to work fine, I will stick with this fs until your needs
> in order to give you logs to better understand what happened.

Glad it worked out for you. I didn't reply because I felt I didn't
know enough to be able to offer any insights.

However, you _are_ aware that btrfs is hardly ready for prime time,
right? If you want stability, then ext3 or ext4 probably are better
choices, despite the kernel 3.6.2 bug. ext3 (and to some extent ext4,
because of its roots in the former) are considered time proven by now
and the tools to work with the file systems are mature; btrfs and
tools are still in heavy development. If you want btrfs's ZFS-like
features and can live with another file system on the root partition
(or lots of fiddling to get it working), want something that is more
ready for prime time and can live with a system that is not purely
Free software, perhaps look into running ZFS through FUSE.

At the very least, if you decide to keep using btrfs, you should make
sure that you have good backups of _everything_ stored on btrfs file
systems. I do believe that everyone is doing their best to avoid bugs
slipping into the code, but that goes for the ext4 developers too.
Nobody _wants_ their name attached to a buggy commit, _particularly_
if that bug causes data loss in production environments.

-- 
Michael Kjörling • http://michael.kjorling.se • michael@kjorling.se
                “People who think they know everything really annoy
                those of us who know we don’t.” (Bjarne Stroustrup)

Re: [RESEND] btrfs corruption / cannot mount

[Chris Samuel]

Hiya Riccardo,

On 02/12/12 19:49, Riccardo Berto wrote:

> I'm a btrfs user since I encountered the ext4 3.6.2 bug and then I
> decided to switch.

You are aware that the ext4 issue you mention only affects people who
turned on journal checksums, and is not turned on by default?

This LWN article has a good summary:

http://lwn.net/Articles/521803/

As Michael wrote btrfs is still considered an experimental filesystem.

All the best,
Chris
-- 
  Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC