Re: parent transid troubles

[Chris Mason <chris.mason@oracle.com>]

Excerpts from Gregory L Shomo's message of 2011-04-19 15:08:13 -0400:
> Hello list-
> 
> Under heavy load (i/o), one of our fileservers lost two drives
> in a raid6 configuration. After the drives were synchronized,
> we can no longer mount the multiple-device btrfs filesystem
> due to (at least) parent transid verification.
> 
> btrfsck built from git commit 1b444cd2e6ab8dcafdd47dbaeaae369dd1517c17
> runs for a while and then aborts on 'failed to find block number'.
> Sample output includes :

Looks like the rebuild gave you older copies of some of the blocks.
btrfsck will exit out pretty early when it sees problems, but I'd say
most of your FS is there.

Can you please do a btrfs-debug-tree /dev/xxx > out, I'd like to see how
far we get.

What errors do you get when trying to mount the FS?

-chris

> 
>   parent transid verify failed on 22569952096256 wanted 176066 found
>   176064
>   parent transid verify failed on 22569952096256 wanted 176066 found
>   176064
>   parent transid verify failed on 20403515183104 wanted 176066 found
>   174710
>   parent transid verify failed on 20403515183104 wanted 176066 found
>   174710
>   parent transid verify failed on 1265784008704 wanted 176066 found
>   175341
>   !-- snip
>   bad block 1099696562176
>   leaf parent key incorrect 1117248647168
>   !-- snip
>   Extent back ref already exists for 1130294538240 parent 0 root 2
>   Extent back ref already exists for 1130295001088 parent 0 root 2
>   !-- snip
>   fs uuid d8464857-db87-412e-9d57-ece6c2054f40
>   chunk uuid 52a652a3-650d-4dd7-aaa2-6f096a714bbf
>           item 0 key (20407857930240 EXTENT_ITEM 4096) itemoff 3944
>   itemsize 51
>                   extent refs 1 gen 165193 flags 2
>                   tree block key (257306671 1 0) level 0
>                   tree block backref root 5
>           item 1 key (20407857934336 EXTENT_ITEM 4096) itemoff 3893
>   itemsize 51
>                   extent refs 1 gen 165308 flags 2
>                   tree block key (257585950 1 0) level 0
>                   tree block backref root 5
>   !-- snip
>   failed to find block number 20407858008064
>   Aborted
> 
> Output is exactly the same when run against both devices, even
> when using 'btrfsck -s1'.
> 
> Should we light a candle and say 'goodbye' to the data or is
> there some hope that btrfsck will be able to help us mount the
> filesystem ?
> 
> Is there any additional information that is useful to the developers ?
> 
> The system is based on fedora-14, btrfs-progs-0.19-12.fc14.x86_64,
> and the arcmsr module (built from the 1.20.0X.15-100729 sources).
> 
> - greg