On Wed, Apr 30, 2025 at 07:48:20PM -0700, H. Peter Anvin wrote: > On 4/25/25 12:59, Theodore Ts'o wrote: > > > > Another use case was Valve who wanted to support Windows games that > > expcted case folding to work. (Microsoft Windows; the gift that keeps > > on giving...) In fact the engineer who worked on case folding was > > paid by Valve to do the work. > > > > That being said, I completely agree with Linus that case insensitivity > > is a nightmare, and I don't really care about performance. The use > > cases where people care about this don't have directories with a large > > number of entries, and we **really** don't want to encourage more use > > of case insensitive lookups. There's a reason why spent much effort > > improving the CLI tools' support for case folding. It's good enough > > that it works for Android and Valve, and that's fine. > > > [...] > > > > Perhaps if we were going to do it all over, we might have only > > supported ASCII, or ISO Latin-1, and not used Unicode at all. But > > then I'm sure Valve or Android mobile handset manufacturers would be > > unhappy that this might not be good enough for some country that they > > want to sell into, like, say, Japan or more generally, any country > > beyond US and Europe. > > > > What we probably could do is to create our own table that didn't > > support all Unicode scripts, but only the ones which are required by > > Valve and Android. But that would require someone willing to do this > > work on a volunteer basis, or confinuce some company to pay to do this > > work. We could probably reduce the kernel size by doing this, and it > > would probably make the code more maintainable. I'm just not sure > > anyone thinks its worthwhile to invest more into it. In fact, I'm a > > bit surprised Kent decided he wanted to add this feature into bcachefs. > > > > Sometimes, partitioning a feature which is only needed for backwards > > compatibiltiy with is in fact the right approach. And throwing good > > money after bad is rarely worth it. > > > > [Yes, I realize I'm really late to weigh in on this discussion] > > It is worth noting that Microsoft has basically declared their "recommended" > case folding (upcase) table to be permanently frozen (for new filesystem > instances in the case where they use an on-disk translation table created at > format time.) As far as I know they have never supported anything other > than 1:1 conversion of BMP code points, nor normalization. > > The exFAT specification enumerates the full recommended upcase table, > although in a somewhat annoying format (basically a hex dump of compressed > data): > > https://learn.microsoft.com/en-us/windows/win32/fileio/exfat-specification
Thanks, I'm adding this to Documentation/filesystems/bcachefs/casefolding.rst
