With the XFS file-system updates for Linux 4.5 there is now better CRC validation during log recovery, log recovery fixes, DAX support fixes, an AGFL size calculation fix, code cleanups, project quota ENOSPC notification via netlink, and tracing/debug improvements. Details on the XFS changes for Linux 4.5 can be found via this pull request.
Of more excitement for end-users are the Flash-Friendly File-System updates for this next version of the Linux kernel. First off, F2FS in Linux 4.5 adds two new ioctls: one for executing online file defragmentation and the other to flush cached data. F2FS also has a speedup when shrinking extent cache entries, handling for if the super-block is broken, refactoring the dirty inode management code, reducing the global lock coverage, and detecting user's idle time. There are also some major bug fixes.
Details on the F2FS changes for Linux 4.5 can be found via this pull request.