Re: btrfs unmountable: read block failed check_tree_block; Couldn't read tree root

[Ansgar Hockmann-Stolle <Ansgar.Hockmann-Stolle@uni-osnabrueck.de>]

Am 27.10.14 um 14:23 schrieb Ansgar Hockmann-Stolle:
> Hi!
>
> My btrfs system partition went readonly. After reboot it doesnt mount
> anymore. System was openSUSE 13.1 Tumbleweed (kernel 3.17.??). Now I'm
> on openSUSE 13.2-RC1 rescue (kernel 3.16.3). I dumped (dd) the whole 250
> GB SSD to some USB file and tried some btrfs tools on another copy per
> loopback device. But everything failed with:
>
> kernel: BTRFS: failed to read tree root on dm-2
>
> See http://pastebin.com/raw.php?i=dPnU6nzg.
>
> Any hints where to go from here?

After an offlist hint (thanks Tom!) I compiled the latest btrfs-progs 
3.17 and tried some more ...

linux:~/bin # ./btrfs --version
Btrfs v3.17
linux:~/bin # ./btrfs-find-root /dev/sda3
Super think's the tree root is at 1015238656, chunk root 20971520
Well block 239718400 seems great, but generation doesn't match, 
have=661931, want=663595 level 0
Well block 239722496 seems great, but generation doesn't match, 
have=661931, want=663595 level 0
Well block 320098304 seems great, but generation doesn't match, 
have=662233, want=663595 level 0
Well block 879341568 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879345664 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879382528 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879398912 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879403008 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879423488 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 879435776 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 880095232 seems great, but generation doesn't match, 
have=663227, want=663595 level 0
Well block 881504256 seems great, but generation doesn't match, 
have=663228, want=663595 level 0
Well block 881512448 seems great, but generation doesn't match, 
have=663228, want=663595 level 0
Well block 936271872 seems great, but generation doesn't match, 
have=663397, want=663595 level 0
Well block 1004490752 seems great, but generation doesn't match, 
have=663571, want=663595 level 0
Well block 1007804416 seems great, but generation doesn't match, 
have=663572, want=663595 level 0
Well block 1012031488 seems great, but generation doesn't match, 
have=663575, want=663595 level 0
Well block 1012396032 seems great, but generation doesn't match, 
have=663575, want=663595 level 0
Well block 1012633600 seems great, but generation doesn't match, 
have=663586, want=663595 level 0
Well block 1012871168 seems great, but generation doesn't match, 
have=663585, want=663595 level 0
Well block 1015201792 seems great, but generation doesn't match, 
have=663588, want=663595 level 0
Well block 1015836672 seems great, but generation doesn't match, 
have=663596, want=663595 level 1
Well block 44132536320 seems great, but generation doesn't match, 
have=658774, want=663595 level 0
Well block 44178280448 seems great, but generation doesn't match, 
have=658774, want=663595 level 0
Well block 87443644416 seems great, but generation doesn't match, 
have=661349, want=663595 level 0
Well block 87514079232 seems great, but generation doesn't match, 
have=651051, want=663595 level 0
Well block 87517679616 seems great, but generation doesn't match, 
have=661349, want=663595 level 0
Well block 98697822208 seems great, but generation doesn't match, 
have=643548, want=663595 level 0
Well block 103285026816 seems great, but generation doesn't match, 
have=661672, want=663595 level 0
Well block 103309553664 seems great, but generation doesn't match, 
have=661674, want=663595 level 0
Well block 103523430400 seems great, but generation doesn't match, 
have=661767, want=663595 level 0
No more metdata to scan, exiting

This line I found interesting because "have" is "want + 1":
Well block 1015836672 seems great, but generation doesn't match, 
have=663596, want=663595 level 1

And here the tail of "btrfs rescue chunk-recover" (full output at 
http://pastebin.com/raw.php?i=1D5VgDxv)

[..]
Total Chunks:	234
   Heathy:	231
   Bad:	3

Orphan Block Groups:

Orphan Device Extents:
Couldn't map the block 1015238656
btrfs: volumes.c:1140: btrfs_num_copies: Assertion `!(ce->start > 
logical || ce->start + ce->size < logical)' failed.
Aborted


Sadly "btrfs check --repair" keep up refusing to do its job.

linux:~ # btrfs check --repair /dev/sda3
enabling repair mode
Check tree block failed, want=1015238656, have=0
Check tree block failed, want=1015238656, have=0
Check tree block failed, want=1015238656, have=0
Check tree block failed, want=1015238656, have=0
Check tree block failed, want=1015238656, have=0
read block failed check_tree_block
Couldn't read tree root
Checking filesystem on /dev/sda3
UUID: 1af256b5-b1ad-443b-aeee-a6853e70b7e2
Critical roots corrupted, unable to fsck the FS
Segmentation fault

Any more hints?

Ciao
	Ansgar