How To Use EXT4's File-System Encryption Feature
The EXT4 file-system in Linux 4.1 brought file-system level encryption support while now with Linux 4.4 it appears to be in better shape with EXT4 maintainer Ted Ts'o recommending any EXT4-encrypted users update their patches against what's to be found in 4.4.
The EXT4 encryption support was developed at Google with plans to likely use it once mature for Android and Chrome OS. Of course, besides needing Linux 4.1+, you also need an updated user-space e2fsprogs for supporting EXT4 encryption.
If you're interested in a brief guide for how to use EXT4's native file-system-level encryption, there's a great guide over on the Quarkslab blog. Likely once Linux 4.4 matures I'll run some performance benchmarks to see how the speed is affected by this native encryption support and possibly compared to dm-crypt.