In this test (attached), the fs was 1G in size, mounted with compression. I used the 2.6.30-r4 kernel, cut copy-pasted the fs/btrfs contents from the btrfs-unstable git tree. After filling a file with zeros until ''No space left on device'', the file was removed. The rm process was killed by the system and crash messages went to /var/log/messages. Another strange thing happened: both df and btrfs-show showed some space left, but the disk was full. Obs: Creating the file with dd resulted in a 994 MB file and with dcfldd in a 22G file. That was because dd uses bs=512 by default and dcfldd uses bs=32k by default Atila