Re: [PATCH v2 1/6] fs: Add case sensitivity info to file_kattr

Theodore Tso
2025-12-12T21:24:31Z

On Fri, Dec 12, 2025 at 10:08:18AM -0500, Chuck Lever wrote:
> The unicode v. ascii case folding information was included just as
> an example. I don't have any use case for that, and as I told Eric,
> those specifics can be removed from the API.
>
> The case-insensitivity and case-preserving booleans can be consumed
> immediately by NFSD. These two booleans have been part of the NFSv3
> and NFSv4 protocols for decades, in order to support NFS clients on
> non-POSIX systems.

I was worried that some clients might be using this information so
they could do informed caching --- i,e., if they have "makefile"
cached locally because the user typed "more < makefile" into their
Windows Command.exe window, and then later on some program tries to
access "Makefile" the client OS might decide that they "know" that
"makefile" and "Makefile" are the same file. But if that's the case,
then it needs to have more details about whether it's ASCII versus
Unicode 1.0 vs Unicode 17.0 case folding that be in use, or there
might be "interesting" corner cases.

Which is why I've gotten increasingly more sympathetic to Linus's
position that case folding is Hot Trash. If it weren't for the fact
that I really wanted to get Android out of using wrapfs (which is an
even greater trash fire), I'd be regretting the fact that I helped to
add insensitive file name support to Linux...

- Ted