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=-0.8 required=3.0 tests=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 5CB42C282DD for ; Tue, 7 Jan 2020 20:04:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3967F2080A for ; Tue, 7 Jan 2020 20:04:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728451AbgAGUEt (ORCPT ); Tue, 7 Jan 2020 15:04:49 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:54363 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728358AbgAGUEt (ORCPT ); Tue, 7 Jan 2020 15:04:49 -0500 Received: from callcc.thunk.org (guestnat-104-133-0-111.corp.google.com [104.133.0.111] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 007K31WJ002663 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 7 Jan 2020 15:03:02 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id B2F684207DF; Tue, 7 Jan 2020 15:03:01 -0500 (EST) Date: Tue, 7 Jan 2020 15:03:01 -0500 From: "Theodore Y. Ts'o" To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Jan Kara , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, linux-cifs@vger.kernel.org, Alexander Viro , Luis de Bethencourt , Salah Triki , Steve French , OGAWA Hirofumi , Greg Kroah-Hartman , Thomas Gleixner , David Sterba , Dave Kleikamp , Anton Altaparmakov , Jan Kara , Eric Sandeen , Namjae Jeon , Pavel Machek , Christoph Hellwig Subject: Re: Unification of filesystem encoding options Message-ID: <20200107200301.GE3619@mit.edu> References: <20200102211855.gg62r7jshp742d6i@pali> <20200107133233.GC25547@quack2.suse.cz> <20200107173842.ciskn4ahuhiklycm@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200107173842.ciskn4ahuhiklycm@pali> Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org On Tue, Jan 07, 2020 at 06:38:42PM +0100, Pali Rohár wrote: > Adding support for case-insensitivity into UTF-8 NLS encoding would mean > to create completely new kernel NLS API (which would support variable > length encodings) and rewrite all NLS filesystems to use this new API. > Also all existing NLS encodings would be needed to port into this new > API. > > It is really something which have a value? Just because of UTF-8? > > For me it looks like better option would be to remove UTF-8 NLS encoding > as it is broken. Some filesystems already do not use NLS API for their > UTF-8 support (e.g. vfat, udf or newly prepared exfat). And others could > be modified/extended/fixed in similar way. You didn't mention ext4 and f2fs, which is using the Unicode code in fs/unicode for its case-folding and normalization support. Ext4 and f2fs only supports utf-8, so using the NLS API would have added no value --- and it as you pointed out, the NLS API doesn't support variable length encoding anyway. In contrast the fs/unicode functions have support for full Unicode case folding and normalization, and currently has the latest Unicode 12.1 tables (released May 2019). What I'd suggest is to create a new API, enhancing the functions in fs/unicode, to support those file systems that need to deal with UTF-16 and UTF-32 for their on-disk directory format, and that we assume that for the most part, userspace *will* be using a UTF-8 encoding for the user<->kernel interface. We can keep the existing NLS interface and mount options for legacy support, but in my opinion it's not worth the effort to try to do anything else. - Ted