The EXT4 changes for Linux 4.4 largely come down to a smothering of bug-fixes for this stable Linxu file-system. In particular, there's also fixes around the EXT4 encryption support and Ted is encouraging any EXT4 encrypted users to update their patches against Linux 4.4 to avoid a memory leak and file-system corruption bug.
A new feature this cycle is supporting CSUM_SEED, for allowing user-space to change the file-system's UUID without rewriting all of the file-system meta-data. More details via today's pull request.
Once Linux 4.4 has seen a few release candidates, I'll be through with my usual Linux file-system benchmarks as always. Until then are also the daily Linux Git benchmarks done at LinuxBenchmarking.com on both Fedora and Ubuntu.