Linux Receiving Generic Casefolding Implementation For File-Systems

In making for easier code re-use among file-systems and allowing a unified implementation to focus on a single code-base for optimizations moving forward, a generic case-folding implementation for Linux file-systems is being prepared for mainline.

EXT4 and F2FS have both supported optional UTF-8 based case-folding support for file/folder names on a per-folder basis going back a year. To date the file-systems have relied upon similar albeit copied implementations of the code while now it's being spun into a generic implementation that can be easily shared between file-systems. Besides avoiding code duplication for UTF8 case-folding, this standardization makes it more easy to optimize it moving forward without having to port any optimizations to the different file-system implementations. The code in its current form should be functionally equivalent to the existing per-filesystem code.

The common implementation and switching F2FS to use the generic support is currently queued in the Flash-Friendly File-System's "dev" branch. If no issues turn up, we can quite likely see this generic case-folding implementation come with Linux 5.10 later this year.