EXT4 Brings New Debugging Ioctls For Linux 5.4
One of the interesting changes with Linux 5.4 for EXT4 is the dropping of a workaround for handling pre-1970 dates that were incorrectly encoded on kernels prior to Linux 4.4 for file timestamps. Since then the kernel has correctly generated the pre-1970 dates and e2fsck is also able to fix the issue now for several years, this workaround has now been dropped -- not that you probably have any pre-1970 timestamps for files on your system. For those curious, the encoding bug led to the timestamps as being in the 24th century.
EXT4 also has several new ioctls with Linux 5.4 for debugging of the extent status cache as well as some documentation improvements. But the rest of the EXT4 work is mostly a collection of random fixes. The complete list of work can be found here.