Trying to mount my ext4 partiton with a 2.6.25 kernel i get this errormessage:
EXT4-fs: hda3: not marked OK to use with test code.
There is a new special flag you have to set to mount development code, so do:
[root]# debugfs -w /dev/hda3 debugfs 1.40.9 (27-Apr-2008) debugfs: set_super_value s_flags 4 debugfs: quit
More info, debugfs, ext4dev, here.