XFS filesystem reports as full though it isn't

[Emmanuel Florac <eflorac@intellique.com>]

I have a 64 bits (x86_64) machine running Linux 2.6.22.19 with a 24TB
XFS filesystem. There are some 15TB of data on it. All is well, no
error except that I can't create a single file (touch foo : no space
left on device). I don't understand what can be going wrong... 

History : this filesystem was extended (xfs_growfs) from 16TB to 24.

I've tought about all XFS problems I can remember of; first, inode
exhaustion :

cluster1:/proc/sys/fs# df -i
Sys. de fich.         Inodes   IUtil.  ILib. %IUti. Mont?sur
/dev/sda1                  0       0       0    -  /
tmpfs                2058624       3 2058621    1% /lib/init/rw
udev                 2058624    1445 2057179    1% /dev
tmpfs                2058624       1 2058623    1% /dev/shm
/dev/mapper/vg0-lv0  25379856384    4287 25379852097    1% /mnt/raid

OK so there's still plenty of inodes available here, that should be OK.
Then maybe we have something wrong elsewhere :

cluster1:/proc/sys/fs# xfs_db -r -c 'freesp -s -a 0' /dev/vg0/lv0
   from      to extents  blocks    pct
      1       1       5       5  71.43
      2       3       1       2  28.57
total free extents 6
total free blocks 7
average free extent size 1.16667

7 blocks free? But there are 9 TB of free space! 

Here is the output from xfs_info /dev/vg0/lv0

meta-data=/dev/vg0/lv0           isize=256    agcount=47,
agsize=137245616 blks =                       sectsz=512   attr=0
data     =                       bsize=4096   blocks=6344964096,
imaxpct=25 =                       sunit=16     swidth=32 blks,
unwritten=1 naming   =version 2              bsize=4096  
log      =internal               bsize=4096   blocks=32768, version=1
         =                       sectsz=512   sunit=0 blks
realtime =none                   extsz=131072 blocks=0, rtextents=0

I fail to see nothing special there however.

The only significant thing I see is that the FS is really close to 16
TB of allocated data (15.7TB). I tried mounting it with "inode64"
option with no more loving.

Any help would be tremendously welcome. Users are starving for more
space and they can't even create a single file! 

-- 
--------------------------------------------------
Emmanuel Florac               www.intellique.com   
--------------------------------------------------