Re: btrfs scrub failing

[Martin Steigerwald <martin@lichtvoll.de>]

Am Sonntag, 3. Januar 2016, 02:02:12 CET schrieb John Center:
> Hi Martin & Duncan,

Hi John,

> Since I had a backup of my data, I first ran "btrfs check -p" on the
> unmounted array.  It first found 3 parent transid errors:
> 
> root@ubuntu:~# btrfs check -p /dev/md126p2
> Checking filesystem on /dev/md126p2
> UUID: 9b5a6959-7df1-4455-a643-d369487d24aa
> parent transid verify failed on 97763328 wanted 33736296 found 181864
> ...
> Ignoring transid failure
> parent transid verify failed on 241287168 wanted 33554449 found 17
> ...
> Ignoring transid failure
> parent transid verify failed on 1016217600 wanted 33556071 found 1639
> ...
> Ignoring transid failure
> 
> Then a huge number of bad extent mismatches:
> 
> bad extent [29360128, 29376512), type mismatch with chunk
> bad extent [29376512, 29392896), type mismatch with chunk
> ...
> bad extent [1039947448320, 1039947464704), type mismatch with chunk
> bad extent [1039948005376, 1039948021760), type mismatch with chunk

Due to these I recommend you redo the BTRFS filesystem using your backup. See 
the other thread where Duncan explained the situation that this may be a sign 
of a filesystem corruption introduced by a faulty mkfs.btrfs version.

I had this yesterday with one of my BTRFS filesystems and these type mismatch 
things didn´t go away with btrfs check --repair from btrfs-tools 4.3.1.

Also

> Next:
> 
> Couldn't find free space inode 1
> checking free space cache [o]
> parent transid verify failed on 241287168 wanted 33554449 found 17
> Ignoring transid failure
> checkingunresolved ref dir 418890 index 0 namelen 15 name umq-onetouch.ko
> filetype 1 errors 6, no dir index, no inode ref
>     unresolved ref dir 418890 index 8 namelen 15 name ums-onetouch.ko
> filetype 1 errors 1, no dir item

the further errors and

[…]
> Once it finished, I tried a recovery mount, which went ok.  Since I already
> had a backup of my data, I tried to run btrfs repair:
> […]
> Then it got stuck on the same error as before.  It appears to be a loop:
> 
> parent transid verify failed on 1016217600 wanted 33556071 found 1639
> Ignoring transid failure
> parent transid verify failed on 1016217600 wanted 33556071 found 1639
> Ignoring transid failure
> ...
[…]
> It's been running this way for over an hour now, never moving on from the
> same errors & the same couple of files.  I'm going to let it run overnight,
> but I don't have a lot of confidence that it will ever exit this loop.  Any
> recommendations as what I should do next?

is a clear sign to me that it likely is more effective to just redo the 
filesystem from scratch than trying to repair it with the limited capabilities 
of current btrfs check command.

So when you have a good backup of your data and want to be confident of a 
sound structure of the filesytem, redo it from scratch with latest btrfs-tools 
4.3.1.

Thats at least my take on this.

Thanks,
-- 
Martin