linux-kernel - Re: vfat: Broken case-insensitive support for UTF-8

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Message-ID: <20200120000931.GX8904@ZenIV.linux.org.uk>
Date:   Mon, 20 Jan 2020 00:09:31 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        "Theodore Y. Ts'o" <tytso@....edu>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Namjae Jeon <linkinjeon@...il.com>,
        Gabriel Krisman Bertazi <krisman@...labora.com>
Subject: Re: vfat: Broken case-insensitive support for UTF-8

On Mon, Jan 20, 2020 at 12:33:48AM +0100, Pali Rohár wrote:

> > Does the behaviour match how Windows handles that thing?
> 
> Linux behavior does not match Windows behavior.
> 
> On Windows is FAT32 (fastfat.sys) case insensitive and file names "č"
> and "Č" are treated as same file. Windows does not allow you to create
> both files. It says that file already exists.

So how is the mapping specified in their implementation?  That's
obviously the mapping we have to match.

> > That's the only reason to support that garbage at all...
> 
> What do you mean by garbage?

Case-insensitive anything... the only reason to have that crap at all
is that native implementations are basically forcing it as fs
image correctness issue.  It's worthless on its own merits, but
we can't do something that amounts to corrupting fs image when
we access it for write.