linux-kernel - Re: [GIT PULL] bcachefs fixes for 6.15-rc4

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Message-ID: <CAHk-=wjGC=QF0PoqUBTo9+qW_hEGLcgb2ZHyt9V8xo5pvtj3Ew@mail.gmail.com>
Date: Sun, 27 Apr 2025 19:39:46 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: Autumn Ashton <misyl@...ggi.es>, Kent Overstreet <kent.overstreet@...ux.dev>, 
	Matthew Wilcox <willy@...radead.org>, "Theodore Ts'o" <tytso@....edu>, linux-bcachefs@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] bcachefs fixes for 6.15-rc4

On Sun, 27 Apr 2025 at 19:22, Eric Biggers <ebiggers@...nel.org> wrote:
>
> I suspect that all that was really needed was case-insensitivity of ASCII a-z.

Yes. That's my argument. I think anything else ends up being a
mistake. MAYBE extend it to the first 256 characters in Unicode (aka
"Latin1").

Case folding on a-z is the only thing you could really effectively
rely on in user space even in the DOS times, because different
codepages would make for different rules for the upper 128 characters
anyway, and you could be in a situation where you literally couldn't
copy files from one floppy to another, because two files that had
distinct names on one floppy would have the *same* name on another
one.

Of course, that was mostly a weird corner case that almost nobody ever
actually saw in practice, because very few people even used anything
else than the default codepage.

And the same is afaik still true on NT, although practically speaking
I suspect it went from "unusual" to "really doesn't happen EVER in
practice".

Extending those mistakes to full unicode and mixing in things like
nonprinting codes and other things have only made things worse.

And dealing with things like ß and ss and trying to make those compare
as equal is a *horrible* mistake. People who really need to do that
(usually for some legalistic local reason) tend to have very specific
rules for sorting anyway, and they are rules specific to particular
situations, not something that the filesystem should even try to work
with.

          Linus