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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 D2CAFC432C0 for ; Thu, 21 Nov 2019 18:29:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B32EB2067D for ; Thu, 21 Nov 2019 18:29:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727007AbfKUS3X (ORCPT ); Thu, 21 Nov 2019 13:29:23 -0500 Received: from outgoing-auth-2.mit.edu ([18.7.34.11]:53288 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726279AbfKUS3X (ORCPT ); Thu, 21 Nov 2019 13:29:23 -0500 X-Greylist: delayed 393 seconds by postgrey-1.27 at vger.kernel.org; Thu, 21 Nov 2019 13:29:22 EST Received: from callcc.thunk.org (guestnat-104-133-8-103.corp.google.com [104.133.8.103] (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 xALIMgeA032373 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 21 Nov 2019 13:22:43 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 0986A4202FD; Thu, 21 Nov 2019 13:22:40 -0500 (EST) Date: Thu, 21 Nov 2019 13:22:40 -0500 From: "Theodore Y. Ts'o" To: "Darrick J. Wong" Cc: linux-ext4 , eric.saint.etienne@oracle.com Subject: Re: [PATCH] tune2fs: prohibit toggling uninit_bg on live filesystems Message-ID: <20191121182240.GJ4262@mit.edu> References: <20191120193255.GF6213@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191120193255.GF6213@magnolia> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Nov 20, 2019 at 11:32:55AM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong > > An internal customer followed an erroneous AskUbuntu article[1] to try to > change the UUID of a live ext4 filesystem. The article claims that you > can work around tune2fs' "cannot change UUID on live fs" error by > disabling uninit_bg, changing the UUID, and re-enabling the feature. > > This led to metadata corruption because tune2fs' journal descriptor > rewrite races with regular filesystem writes. Therefore, prevent > administrators from turning on or off uninit_bg on a mounted fs. > > [1] https://askubuntu.com/questions/132079/how-do-i-change-uuid-of-a-disk-to-whatever-i-want/195839#459097 > > Signed-off-by: Darrick J. Wong Thanks, applied. - Ted