From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B40D5C3F2D1 for ; Mon, 2 Mar 2020 17:14:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F21221775 for ; Mon, 2 Mar 2020 17:14:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WzhlaRqk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727329AbgCBROd (ORCPT ); Mon, 2 Mar 2020 12:14:33 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:34968 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726451AbgCBROc (ORCPT ); Mon, 2 Mar 2020 12:14:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=j2hxqpKaUS+Roc4f5i/Vccd0HuWME03vKc4/t6bqvZU=; b=WzhlaRqkrARIRkhmc9tWzVFJru i7i9Mnd6DjL0eCkjZCR93mH7tw1DArkNfxnqD/UZBPA2EMwBYaWir3uj/9HwHyhreByb0cbdrid58 /36LpKspqV4ECkhnZKXAresU2d+xpiUm9/yeUIe3cDFg2TmjkJ2bX4/vScW8YZZ1vfK2a61ciZHiS 5Bb9GZ7mbOUjrtIk1ZQY+mjbiwiMWDNl2qV6ed7fiSvcLL06sysh6IJ4onP146So5JuZnbSZ8Pj/n bdCjT7qXl85BPYOqIXHe4cuUSEyh48bGL5/OsUs68gnlYIIFeGR4DKJuWAvHm+OwgjOCSAu+CymcJ uzCreRSQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j8oeF-0005xZ-8l; Mon, 02 Mar 2020 17:14:31 +0000 Date: Mon, 2 Mar 2020 09:14:31 -0800 From: Matthew Wilcox To: Al Viro Cc: lampahome , linux-fsdevel@vger.kernel.org Subject: Re: why do we need utf8 normalization when compare name? Message-ID: <20200302171431.GQ29971@bombadil.infradead.org> References: <20200302125432.GP29971@bombadil.infradead.org> <20200302152818.GN23230@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200302152818.GN23230@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.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.