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 4B889C33C8C for ; Mon, 6 Jan 2020 19:46:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 260972072C for ; Mon, 6 Jan 2020 19:46:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726788AbgAFTqi convert rfc822-to-8bit (ORCPT ); Mon, 6 Jan 2020 14:46:38 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:36250 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726657AbgAFTqi (ORCPT ); Mon, 6 Jan 2020 14:46:38 -0500 Received: from localhost (unknown [IPv6:2610:98:8005::147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: krisman) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id C2936291A19; Mon, 6 Jan 2020 19:46:36 +0000 (GMT) From: Gabriel Krisman Bertazi To: Pali =?utf-8?Q?Roh=C3=A1r?= Cc: Namjae Jeon , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, gregkh@linuxfoundation.org, valdis.kletnieks@vt.edu, hch@lst.de, sj1557.seo@samsung.com, linkinjeon@gmail.com, tytso@mit.edu Subject: Re: [PATCH v9 10/13] exfat: add nls operations Organization: Collabora References: <20200102082036.29643-1-namjae.jeon@samsung.com> <20200102082036.29643-11-namjae.jeon@samsung.com> <20200105165115.37dyrcwtgf6zgc6r@pali> Date: Mon, 06 Jan 2020 14:46:33 -0500 In-Reply-To: <20200105165115.37dyrcwtgf6zgc6r@pali> ("Pali =?utf-8?Q?Roh?= =?utf-8?Q?=C3=A1r=22's?= message of "Sun, 5 Jan 2020 17:51:15 +0100") Message-ID: <85woa4jrl2.fsf@collabora.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Pali Rohár writes: > What do you think what should kernel's exfat driver do in this case? > > To prevent such thing we need to use some kind of Unicode normalization > form here. > > CCing Gabriel as he was implementing some Unicode normalization for ext4 > driver and maybe should bring some light to new exfat driver too. We have an in-kernel implementation of the canonical decomposition normalization (NFD) in fs/unicode, which is what we use for f2fs and ext4. It is heated argument what is the best form for filesystem usage, and from what I researched, every proprietary filesystem does a different (and crazy in their unique way) thing. For exfat, even though the specification is quite liberal, I think the reasonable answer is to follow closely whatever behavior the Windows implementation has, whether it does normalization at all or not. Even if it is just an in-memory format used internally for lookups, assuming a different format or treating differently invalid file names can result in awkward results in a filesystem created on another operating system, like filename collisions or false misses in lookups. -- Gabriel Krisman Bertazi