ENOSPC but df and df -i show free space

[Andy Isaacson]

% touch /d1/tmp/foo
touch: cannot touch `/d1/tmp/foo': No space left on device
% df /d1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/vg0-d1   943616000 904690332  38925668  96% /d1
% df -i /d1
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/mapper/vg0-d1   167509008 11806336 155702672    8% /d1
% sudo xfs_growfs -n /d1
meta-data=/dev/mapper/vg0-d1     isize=256    agcount=18, agsize=13107200 blks
         =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=235929600, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal               bsize=4096   blocks=25600, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
% grep d1 /proc/mounts
/dev/mapper/vg0-d1 /d1 xfs rw,relatime,attr2,noquota 0 0

Obviously I'm missing something, but what?

Nothing relevant in dmesg that I can see.  The filesystem started out at
200 GB and has been xfs_growfs'd in 100GB increments up to its current
size of 900 GB.

x86_64 2.6.38-rc3-00019-gafe8a88 on a quad-core i7 with 12GB RAM, on DM
on AHCI SATA.

-andy