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=-4.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 7B041C11F68 for ; Thu, 1 Jul 2021 00:24:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5910461466 for ; Thu, 1 Jul 2021 00:24:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237828AbhGAA0e (ORCPT ); Wed, 30 Jun 2021 20:26:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:54422 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236734AbhGAA0d (ORCPT ); Wed, 30 Jun 2021 20:26:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPS id 44DE761452 for ; Thu, 1 Jul 2021 00:24:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625099044; bh=qGjmhDctBZGIFbOtIEBW2NamNRcEt+/mXssFSFIWmeE=; h=From:To:Subject:Date:In-Reply-To:References:From; b=nEhXQRLqSiDTpxH/Ues/+nhQb8AsYiV3Ry1Fobn3WzZjQQrRyRsRQmt5KQ426Kzoe fR8AhbMlBDd8t5JqGajnHRkMhqD03k9BmglACviiXkMOsWx4g1AbRBkgvasyaaWfQL 2evlTzxQjDeQVDfu8895wqLrp1iCI7FUqNhfEAP3STh6zx9H/G7r2GG4qcsjQkjxuE sZBob/4a0gtgZW220DWwC2wBHXJgvl+BYIngDlPYUckkcCsyVHXpdBckg0Lih5WBll iBG9PKmY13UGpPoNKFtKfMgVhjUe5widQgmrUj5nStGzYHHcxsQVpdZsBfQ58k0kBf q1HdSeBrb8fzA== From: bugzilla-daemon@bugzilla.kernel.org To: linux-ext4@vger.kernel.org Subject: [Bug 213627] Fail to read block descriptors data of ext4 filesystem Date: Thu, 01 Jul 2021 00:24:04 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo fs_ext4@kernel-bugs.osdl.org X-Bugzilla-Product: File System X-Bugzilla-Component: ext4 X-Bugzilla-Version: 2.5 X-Bugzilla-Keywords: X-Bugzilla-Severity: high X-Bugzilla-Who: tytso@mit.edu X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: fs_ext4@kernel-bugs.osdl.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org https://bugzilla.kernel.org/show_bug.cgi?id=3D213627 Theodore Tso (tytso@mit.edu) changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |tytso@mit.edu --- Comment #2 from Theodore Tso (tytso@mit.edu) --- I'm guessing that it's your snapshot driver which is buggy. Certainly, if= you take a snapshot using LVM, things work fine. e.g.: # mke2fs -t ext4 /dev/cwcc-wg/scratch # mount -t ext4 /dev/cwcc-wg/scratch /mnt # cp -r /etc /mnt # lvcreate --snapshot -n snap -L 5G cwcc-wg/scratch # e2fsck -fn /dev/cwcc-wg/snap You can see everything that has changed via a command such as "git log v5.0..v5.3 block fs/ext4". In terms of what might be a relevant change, without understanding how your snapshot driver works, your guess is probably going to be better than mine --- since you have access to your snapshot dri= ver and know how it works. When you say that your driver "bypasses read/write calls to system block driver", I'm not 100% sure how it works, but at a guess, some things I'd lo= ok at are: (a) ext4 uses the buffer cache to read/write metadata blocks. May= be your driver isn't properly intercepting buffer cache reads/writes? (b) E= xt4 at mount time reads the superblock via the buffer cache with the block size= set to 1k; and then after it determines the block size of the file system (say, 4k), it switches the block size of the buffer cache to the block size of the file system. Ext[234] has been doing this for decades, but depending on = how your snapshot driver is working, perhaps there is some change in the how the buffer cache works which is confusing your driver. Sorry I can't help more. --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=