Re: why do we need utf8 normalization when compare name?

[Matthew Wilcox <willy@infradead.org>]

On Mon, Mar 02, 2020 at 03:28:18PM +0000, Al Viro wrote:
> Why the hell do we need case-insensitive filesystems in the first place?
> I have only heard two explanations:
> 	1) because the layout (including name equivalences) is fixed by
> some OS that happens to be authoritative for that filesystem.  In that
> case we need to match the rules of that OS, whatever they are.  Unicode
> equivalence may be an interesting part of _their_ background reasons
> for setting those rules, but the only thing that really matters is what
> rules have they set.
> 	2) early Android used to include a memory card with VFAT on
> it; the card is long gone, but crapplications came to rely upon having
> that shit.  And rather than giving them a file on the normal filesystem
> with VFAT image on it and /dev/loop set up and mounted, somebody wants
> to use parts of the normal (ext4) filesystem for it.  However, the
> same crapplications have come to rely upon the case-insensitive (sensu
> VFAT) behaviour there, so we must duplicate that vomit-inducing pile
> of hacks on ext4.  Ideally - with that vomit-induc{ing,ed} pile
> reclassified as a generic feature; those look more respectable.
> 
> (1) is reasonable enough, but belongs in specific weird filesystems.
> (2) is, IMO, a bad joke.
> 
> Does anybody know of any other reasons?

I've heard it was primarily developed to help port an ecosystem known
for prioritising shipping-on-time over quality-of-code from Windows to
Linux.  I'm not sure why a variant of #2 wasn't a solution they used.
I'm not a fan of having case-insensitive unicode tables in the kernel.