As a follow-up on the discussions held in this list after Ted's proposal on case-insensitive support for ext4 last year, I've implemented a my version of it to learn my way through the ext4 code, and to get started on the task. As my goal would be a slightly more complex approach, with at least UTF-8 support for lookups, I'd like to hear from you about my current implementation and the following proposal, as well as if there is anyone currently working on anything like this, so we could coordinate efforts. Regarding the Unicode proposal (shivers), I am aware of Ben and Olaf's proposal from 2014, and I plan to work on top of that to get it updated and upstream. Please, let me know your thoughts. * Current Implementation Simple learning experience to get the wheel spinning, based on Ted Ts'o initial proposal back in 2016 [1]. It supports ASCII-case folding only and doesn't rely on on-disk modifications. Available at: https://git.collabora.com/cgit/user/krisman/linux.git/log/?h=ext4-insensitive - Implemented as a mount option, called ignorecase, which enables insensitive lookups for the entire filesystem. A look-up will first attempt the htree search for an exact-case match and if that fails, fallback to a performing the expensive linear search. - ASCII case-folding only. - No on-disk format changes. - If two files differ only by case, an exact-case lookup will return the expected file. A non-exact-case lookup result will be unpredictable as to which file is returned (depends on the order on-disk). * Proposal - Make insensitive lookups enabled on a per-directory basis via an attribute. - Support UTF-8 encoding in-kernel for case folding. - sb will store the information required for unicode versioning and encoding. - Empty directories are optimized with an insensitive hash for htree lookups. - Fallback to linear searches on directories not optimized. [1] https://www.spinics.net/lists/linux-ext4/msg54279.html -- Gabriel Krisman Bertazi
