From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id 685817F37 for ; Mon, 4 Jan 2016 17:52:46 -0600 (CST) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay2.corp.sgi.com (Postfix) with ESMTP id 24A26304066 for ; Mon, 4 Jan 2016 15:52:46 -0800 (PST) Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net [150.101.137.141]) by cuda.sgi.com with ESMTP id lykMh2Zm4qHUnwZD for ; Mon, 04 Jan 2016 15:52:37 -0800 (PST) Date: Tue, 5 Jan 2016 10:51:25 +1100 From: Dave Chinner Subject: Re: [PATCH 05/76] libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct Message-ID: <20160104235125.GG19802@dastard> References: <20151219085622.12713.88678.stgit@birch.djwong.org> <20151219085655.12713.60317.stgit@birch.djwong.org> <20160103121525.GB28429@infradead.org> <20160104221218.GB28330@birch.djwong.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160104221218.GB28330@birch.djwong.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: "Darrick J. Wong" Cc: Christoph Hellwig , xfs@oss.sgi.com On Mon, Jan 04, 2016 at 02:12:18PM -0800, Darrick J. Wong wrote: > On Sun, Jan 03, 2016 at 04:15:25AM -0800, Christoph Hellwig wrote: > > On Sat, Dec 19, 2015 at 12:56:55AM -0800, Darrick J. Wong wrote: > > > Because struct xfs_agfl is 36 bytes long and has a 64-bit integer > > > inside it, gcc will quietly round the structure size up to the nearest > > > 64 bits -- in this case, 40 bytes. This results in the XFS_AGFL_SIZE > > > macro returning incorrect results for v5 filesystems on 64-bit > > > machines (118 items instead of 119). As a result, a 32-bit xfs_repair > > > will see garbage in AGFL item 119 and complain. > > > > > > Therefore, tell gcc not to pad the structure so that the AGFL size > > > calculation is correct. > > > > Do you have a testcase for this? > > Not much aside from: > > 0. Build kernel/xfsprogs with RFCv4 patches on a 64bit machine. > 1. Build kernel/xfsprogs with RFCv4 patches on a 32bit machine. > 2. Format a XFS with reflink and rmap on a 64-bit machine, so that the AGFL > size is maximized. > 3. Mount FS and create a reflinked file. > 4. Unmount and xfs_repair with the 32-bit build. > > I guess we could create a program that compares all the known sizeof(struct > xfs_disk_object) values against known good values and stuff that into the > xfsprogs build process. There's an xfstest for that: xfs/122. It notruns on my systems since the big xfsprogs build/header rework, and I haven't found the time to work out what it needs to run again. Also, I don't think it covers the AGFL structure, because that it relatively new and the test doesn't check any of the v5 specific structures.... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs