> I did not check myself but it seems the Internet thinks that dragonflybsd
> has ext2/3/4 support all backed into the ext2fs implementation which is
> probably close to ours. If that is true there may be a place where a lot
> of the code can be picked up.

DragonflyBSD is currently using the FreeBSD ext2fs code, which has some 
limited ext4fs support.