can't read superblock on a xfs partition

[Nicolas Meaux <nmeaux@xxxxxxxxxxxx>]

Hi,

I have a big problem with a xfs partition, i have made a very big 
mistake when i was typing the xfs_growfs command and now the partition 
are not able to mount due to a superblock failure, of course i didn't 
made backup :/

- I use xfs over lvm with xfs version 2.6.25 and try xfs 2.7.3too

The mistake :
- I made :
lvextend -L +100G /dev/jbod2/export
xfs_growfs /export
*sic*
( in place of : xfs_growfs /dev/jbod2/export )

My xfs partition was previously mounted on /export

So ... i start to panic, and then to think :
- I do a :
xfs_repair -n -o assume_xfs /dev/jbod2/export
( with alternatively -n and -o assume_xf options )

The output is :

Phase 1 - find and verify superblock...
error reading superblock 3 -- seek to offset 82431049728 failed
couldn't verify primary superblock - bad magic number !!!

attempting to find secondary superblock...
...
...
...
found candidate secondary superblock...
error reading superblock 3 -- seek to offset 82431049728 failed
unable to verify superblock, continuing...
...
...
...
found candidate secondar
y superblock...
error reading superblock 3 -- seek to offset 82431049728 failed
unable to verify superblock, continuing...
...
...
...
Sorry, could not find valid secondary superblock
Exiting now.


I have this message in my syslog :
attempt to access beyond end of device
dm-0: rw=0, want=1717313536, limit=121118720
I/O error in filesystem ("dm-0") meta-data dev dm-0 block 0x665c1fff 
   ("xfs_read_buf") error 5 buf count 512
XFS: size check 2 failed

# xfs_check /dev/jbod2/export
XFS: totally zeroed log
can't seek in filesystem at bb 125297920
can't read block 0 for directory inode 167128840
no . entry for directory 167128840
no .. entry for directory 167128840
/bin/xfs_check: line 56:  5657 Segmentation fault      xfs_db$DBOPTS -i 
-p xfs_check -c "check$OPTS" $1

# xfs_admin -l -u /dev/jbod2/export
can't seek in filesystem at bb 160998144
can't read superblock for AG 3
failed to read label in AG 3
can't seek in filesystem at bb 160998144
can't read superblock for AG 3
failed to read UUID from AG 3


Did a small solution exist to recover of this superblock failure or will 
i have to considere that my data are lost ?  I apologize for these 
questions, i havn't a lot of experience in xfs use, but if anyone could 
give me a solution, i will greatly appreciate it.

Regards,

Nicolas