From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sat, 29 Mar 2008 18:30:33 -0700 (PDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m2U1TvW2018902 for ; Sat, 29 Mar 2008 18:29:58 -0700 Received: from sandeen.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 894BB8BE0C2 for ; Sat, 29 Mar 2008 18:30:33 -0700 (PDT) Received: from sandeen.net (sandeen.net [209.173.210.139]) by cuda.sgi.com with ESMTP id tGF1fsaADfsEYM3T for ; Sat, 29 Mar 2008 18:30:33 -0700 (PDT) Message-ID: <47EEED18.9090206@sandeen.net> Date: Sat, 29 Mar 2008 20:30:00 -0500 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: [patch] detect and correct bad features2 superblock field References: <20080220054041.GM155407@sgi.com> In-Reply-To: <20080220054041.GM155407@sgi.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: David Chinner Cc: xfs-dev , xfs-oss David Chinner wrote: > There is a bug in mkfs.xfs that can result in writing the features2 > field in the superblock to the wrong location. This only occurs > on some architectures, typically those with 32 bit userspace and > 64 bit kernels. > > This patch detects the defect at mount time, logs a warning > such as: > > XFS: correcting sb_features alignment problem > > in dmesg and corrects the problem so that everything is OK. > it also blacklists the bad field in the superblock so it does > not get used for something else later on. ... > /* > + * Check for a bad features2 field alignment. This happened on > + * some platforms due to xfs_sb_t not being 64bit size aligned > + * when sb_features was added and hence the compiler put it in > + * the wrong place. > + * > + * If we detect a bad field, we or the set bits into the existing > + * features2 field in case it has already been modified and we > + * don't want to lose any features. Zero the bad one and mark > + * the two fields as needing updates once the transaction subsystem > + * is online. > + */ > + if (xfs_sb_has_bad_features2(sbp)) { > + cmn_err(CE_WARN, > + "XFS: correcting sb_features alignment problem"); > + sbp->sb_features2 |= sbp->sb_bad_features2; > + sbp->sb_bad_features2 = 0; > + update_flags |= XFS_SB_FEATURES2 | XFS_SB_BAD_FEATURES2; > + } Hm, the other problem here may be that if we zero bad_features2, then any older kernel will mount up as attr2... and run into the corruption problem I found on F8... Should we make features2 and bad_features2 match rather than zeroing bad_features2? -Eric