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=-3.8 required=3.0 tests=BAYES_00, 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 B35A1C4363A for ; Tue, 27 Oct 2020 19:36:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F4E32222C for ; Tue, 27 Oct 2020 19:36:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2896816AbgJ0Tgp (ORCPT ); Tue, 27 Oct 2020 15:36:45 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:48203 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2504087AbgJ0Tgo (ORCPT ); Tue, 27 Oct 2020 15:36:44 -0400 Received: from callcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 09RJaXEt029645 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 27 Oct 2020 15:36:34 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id CB01F420107; Tue, 27 Oct 2020 15:36:33 -0400 (EDT) Date: Tue, 27 Oct 2020 15:36:33 -0400 From: "Theodore Y. Ts'o" To: Edward Shishkin Cc: David Niklas , reiserfs-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: PROBLEM: Reiser4 hard lockup Message-ID: <20201027193633.GE5691@mit.edu> References: <20201025090422.D80F56FB40E1@huitzilopochtli.metztli-it.com> <20201025210758.034aa947@Phenom-II-x6.niklas.com> <2e2f8dc4-a48e-f09c-3f41-5dfa7f9a6387@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e2f8dc4-a48e-f09c-3f41-5dfa7f9a6387@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 27, 2020 at 01:53:31AM +0100, Edward Shishkin wrote: > > > reiser4progs 1.1.x Software Framework Release Number (SFRN) 4.0.1 file > > > system utilities should not be used to check/fix media formatted 'a > > > priori' in SFRN 4.0.2 and vice-versa. > > > > Honestly, this is the first time I've heard about a Linux FS having > > versioning other than a major one > > This is because, unlike other Linux file systems, reiser4 is a > framework. > > In vanilla kernel having a filesystem-as-framework is discouraged for > ideological reasons. As they explained: "nobody's interested in > plugins". A huge monolithic mess without any internal structure - > welcome :) I wouldn't call it an ideological problem, but more about wanting to assure interoperability issues and wanting to reduce confusion on the part of users, especially if images get moved between systems. There is also plenty of way of introducing internal structure and code cleanliness without going completely undisciplined with respect to on-disk format extensions. :-) Finally, I'll note that ext 2/3/4 does have a rather fine-grained set of feature flags, with specific rules about what the kernel --- and e2fsck --- should do if it finds a feature bit it doesn't understand in the incompat, ro_compat, and compat feature flags set. This is especially helpful since we have multiple implementations of ext 2/3/4 out there (in FreeBSD, the GRUB bootloader, GNU HURD, Fuchsia, etc.) and so using feature bits allow for safe and reliable interoperability with the user being warned if they can safely only mount the file system read-only, or not at all, if the file system has some new feature that their current OS version does not support. We can also give appropriate warnings if they are using an insufficiently recent version of the userspace tools. Cheers, - Ted