no space to remove a file

["Toralf Förster" <toralf.foerster@gmx.de>]

While running trinity within a user mode linux image which has the same BTRFS filesystem from the host
mounted both via NFS and hostfs (that FS itself was created within a file at a ramdisk at the host side) 
I observed from my control script these messages :

rm: cannot remove ‘/mnt/trinity/w/inux’: No space left on device
rm: cannot remove ‘/mnt/trinity/w/$’: No space left on device
rm: cannot remove ‘/mnt/trinity/w/\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\211\271\271\340\340\211\n\277’: No space left on device
rm: cannot remove ‘/mnt/trinity/w/\020’: No space left on device
mkdir: cannot create directory ‘/mnt/trinity/w’: File exists
chmod: changing permissions of ‘/mnt/trinity/v/victims’: No space left on device
chmod: changing permissions of ‘/mnt/trinity/v/victims/d01’: No space left on device


Well, the file system is full:
$> df -m
...
/dev/loop0           257   245         9  97% /mnt/trinity

but why does rm fail with that messages ?
And chmod too ?

FWIW host kernel is 3.8.9, UML guest runs 3.9-rc8-..., OS is Gentoo stable at each system.


-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3