Hi,

Env:
Ubuntu Server x86-64, 2.6.32-24
/ on ext4
data on iSCSI target + btrfs + compression

History:
FS (data) frozen; can't read(list) files from subdir, can't write file.
Sync hung.
Ctrl-Alt-Del, nothing. (more times) :(
Power off
Restart, segfault

# mount -t btrfs -o compress /dev/vdb1 /usr/local/backups
Segmentation fault

log: