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 6F6B1C46466 for ; Tue, 6 Oct 2020 03:18:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32B5B20782 for ; Tue, 6 Oct 2020 03:18:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726670AbgJFDSv (ORCPT ); Mon, 5 Oct 2020 23:18:51 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:47075 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725917AbgJFDSv (ORCPT ); Mon, 5 Oct 2020 23:18:51 -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 0963IYat000571 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 5 Oct 2020 23:18:35 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 2C0AA420107; Mon, 5 Oct 2020 23:18:34 -0400 (EDT) Date: Mon, 5 Oct 2020 23:18:34 -0400 From: "Theodore Y. Ts'o" To: "Darrick J. Wong" Cc: Josh Triplett , Linus Torvalds , Andreas Dilger , Jan Kara , Linux Kernel Mailing List , linux-ext4@vger.kernel.org Subject: Re: ext4 regression in v5.9-rc2 from e7bfb5c9bb3d on ro fs with overlapped bitmaps Message-ID: <20201006031834.GA5797@mit.edu> References: <20201005081454.GA493107@localhost> <20201005173639.GA2311765@magnolia> <20201006003216.GB6553@localhost> <20201006025110.GJ49559@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201006025110.GJ49559@magnolia> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Mon, Oct 05, 2020 at 07:51:10PM -0700, Darrick J. Wong wrote: > > > Could /somebody/ please document the ondisk format changes that are > > > associated with this feature? > > > > I pretty much had to sort it out by looking at a combination of > > e2fsprogs and the kernel, and a lot of experimentation, until I ended up > > with something that the kernel was completely happy with without a > > single complaint. > > > > I'd be happy to write up a summary of the format. > > Seems like a good idea, particularly since you're asking for a format > change that requires kernel support and the ondisk format documentation > lives under Documentation/. That said... > > If you set up the rest of the metadata consistently with it (for > > instance, 0 free blocks and 0 free inodes), you'll only get a single > > complaint, from the e2fsck equivalent of block_validity. See > > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=956509 for details on > > that; > > ...Ted shot down this whole thing six months ago. > > The Debian bug database is /not/ the designated forum to discuss changes > to the ondisk format; linux-ext4 is. What Josh is proposing I'm pretty sure would also break "e2fsck -E unshare_blocks", so that's another reason not to accept this as a valid format change. As far as I'm concerned, contrib/e2fsdroid is the canonical definition of how to create valid file systems with shared_blocks. - Ted