Filesystem not mountable after reset, bad tree block

Filesystem not mountable after reset, bad tree block

[Michael Andreen]

Hi,

Today one of my machines (running kernel 3.0.6) locked up, sadly the monitor 
was stuck in power saving mode and no access over network so not sure exactly 
what happened. After restarting the machine, the root filesystem is no longer 
mountable the following output appears: 

device label SSD devid 1 transid 507930 /dev/sdb2
btrfs bad tree block start 0 188205998080
btrfs bad tree block start 0 188205998080
btrfs bad tree block start 0 188205998080
btrfs: open_ctree failed

I downloaded the latest btrfs-progs, but getting similar output from several 
of the programs:

# ./btrfs-debug-tree /dev/sdb2
Check tree block failed, want=188205998080, have=0
Check tree block failed, want=188205998080, have=0
Check tree block failed, want=188205998080, have=0
Check tree block failed, want=188205998080, have=0
Check tree block failed, want=188205998080, have=0
read block failed check_tree_block
btrfs-debug-tree: disk-io.c:447: find_and_setup_root: Assertion `!(!root-
>node)' failed.
Aborted

The find-root program seems to think there is a root (and poentially some 
older roots?), but not sure how to use that information.

# ./find-root /dev/sdb2 
Super think's the tree root is at 131212083200, chunk root 20983808
Well block 13856997376 seems great, but generation doesn't match, have=321485, 
want=507930
Well block 16362573824 seems great, but generation doesn't match, have=317992, 
want=507930
Well block 16367947776 seems great, but generation doesn't match, have=321490, 
want=507930
Well block 36317024256 seems great, but generation doesn't match, have=195981, 
want=507930
Well block 39698722816 seems great, but generation doesn't match, have=273675, 
want=507930
Well block 39714439168 seems great, but generation doesn't match, have=320627, 
want=507930
Well block 43016519680 seems great, but generation doesn't match, have=272156, 
want=507930
Well block 43031748608 seems great, but generation doesn't match, have=302652, 
want=507930
Well block 47617982464 seems great, but generation doesn't match, have=274708, 
want=507930
Found tree root at 131212083200

Anything else I can do to debug this or potentially recover a few bits before 
reformatting?

/Michael

Re: Filesystem not mountable after reset, bad tree block

[Kai Krakow]

Hi!

Michael Andreen <harv@ruin.nu> schrieb:
> The find-root program seems to think there is a root (and poentially some
> older roots?), but not sure how to use that information.
[...]
> Anything else I can do to debug this or potentially recover a few bits
> before reformatting?

You could try the recovery programs from Josefs btrfs-progs tree[1]. You 
could also try using kernel 3.2 which allows mounting in recovery mode. This 
mode tries to find an older tree root. But I think your kernel did not keep 
tree root backups for this purpose as it is AFAIR a feature of later 
kernels.

Better use a newer kernel - best use 3.2. There are bunch of fixes which 
improve the situation with lost file systems after unexpected reboots or 
power outages.

HTH
Kai

[1] https://github.com/josefbacik/btrfs-progs

Re: Filesystem not mountable after reset, bad tree block

[Hugo Mills]

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On Sat, Jan 07, 2012 at 01:05:08PM +0100, Kai Krakow wrote:
> Hi!
> 
> Michael Andreen <harv@ruin.nu> schrieb:
> > The find-root program seems to think there is a root (and poentially some
> > older roots?), but not sure how to use that information.
> [...]
> > Anything else I can do to debug this or potentially recover a few bits
> > before reformatting?
> 
> You could try the recovery programs from Josefs btrfs-progs tree[1].

   You'll find what little documentation we have on the restore
program here:

   http://btrfs.ipv5.de/index.php?title=Restore

   With luck, you'll just need to run restore, but there's also a
little bit on how to read and use the output of find-root.

   Hugo.

> You 
> could also try using kernel 3.2 which allows mounting in recovery mode. This 
> mode tries to find an older tree root. But I think your kernel did not keep 
> tree root backups for this purpose as it is AFAIR a feature of later 
> kernels.
> 
> Better use a newer kernel - best use 3.2. There are bunch of fixes which 
> improve the situation with lost file systems after unexpected reboots or 
> power outages.
> 
> HTH
> Kai
> 
> [1] https://github.com/josefbacik/btrfs-progs
> 

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
     --- Computer Science is not about computers,  any more than ---     
                     astronomy is about telescopes.                      

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Re: Filesystem not mountable after reset, bad tree block

[Michael Andreen]

On Saturday 07 January 2012 17:01:40 Hugo Mills wrote:
> On Sat, Jan 07, 2012 at 01:05:08PM +0100, Kai Krakow wrote:
> > 
> > You could try the recovery programs from Josefs btrfs-progs tree[1].
> 
>    You'll find what little documentation we have on the restore
> program here:
> 
>    http://btrfs.ipv5.de/index.php?title=Restore
> 
>    With luck, you'll just need to run restore, but there's also a
> little bit on how to read and use the output of find-root.

Thanks, it worked very well. Almost disappointed that it managed to recover 
all the junk accumulated through the years ;)

It had some problems on certain parts, crashing or just exiting with message 
about "extent buffer leak", but rerunning it without -o made it continue past 
that point. Not sure if that's normal or known, I'll keep the image around and 
see if I have time to debug it.

/Michael