The Ext4 file system is standard file system for Linux (recent Ubuntu, and somewhat old Fedora). It is the successor of the Ext3 file system.

It has journaling, larger file system volumes, and improved timestamp etc features.

The NetBSD kernel support and accompanying userland code should be written.

It is not clear at the moment if this should be done by working on the existing ext2 code or not, and if not, whether it should be integrated with the ufs code or not.