Re: volume broken? btrfsck fails

[Thomas Kuther <gimpel@sonnenkinder.org>]

On Di, 06.07.10 20:16 Chris Mason <chris.mason@oracle.com> wrote:

> On Sat, Jun 26, 2010 at 03:15:04PM -0700, Yee-Ting Li wrote:
> > Hi,
> > 
> > i think my btrfs volume is hosed.... it mounts okay, but iostat
> > shows /dev/sdg on 100% load. dmesg shows lots of 'parent transid
> > verify failed on x wanted y found z'. then after a while i can't
> > read from it (access to the filesystem freezes).
> > 
> > the machine had crashed (prob from some other process), and upon
> > reboot i've been experience this problem since.
> > 
> > can anyone provide any guidance in how to proceed?
> 
> These are definitely corruptions, and they probably came from the
> crash. Can you tell me more about the crash? (Power failure, what is
> the storage underneath etc, what are the write cache settings).  We
> don't expect these kinds corruptions to happen.
> 
> Yan Zheng is making a lot of progress on btrfsck, but I don't think
> you'll want to be one of the first testers there.  I can definitely
> help copy things off if you're having trouble accessing the FS.
> 
> -chris

Hello Chris,

sorry if I'm hijacking this thread. I got a similar problem, probably
caused by a system crash due to faulty/badly timed memory dimms. The
system suddenly hardlocked during write activity.

- kernel is 2.6.35
- btrfs on top of a md raid5, which looks healthy. Desktop SATA disks.

# cat /proc/mdstat|grep -A1 md0
md0 : active raid5 sdb1[0] sdd1[1] sdc1[2]
      2930271872 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

# btrfsck
usage: btrfsck dev
Btrfs v0.19-16-g075587c-dirty

# btrfsck /dev/md0
parent transid verify failed on 2419218964480 wanted 127839 found 127260
parent transid verify failed on 2419218964480 wanted 127839 found 127260
parent transid verify failed on 2419218915328 wanted 127839 found 127260
parent transid verify failed on 2419218915328 wanted 127839 found 127260
parent transid verify failed on 2419214266368 wanted 127839 found 127837
parent transid verify failed on 2419214266368 wanted 127839 found 127837
parent transid verify failed on 2419214266368 wanted 127839 found 127837
Segmentation fault

Mount endlessly loops, like explained in this thread.

If there is a way, I would really like some aid copying the data off.
The backup is quite out of date, shame on me.

Best regards,
Thomas