From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id n7DDkkDx024291 for ; Thu, 13 Aug 2009 08:46:56 -0500 Received: from mail.bgs.hu (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with SMTP id 37A313C7DB9 for ; Thu, 13 Aug 2009 06:47:19 -0700 (PDT) Received: from mail.bgs.hu (bgs.hu [195.228.254.245]) by cuda.sgi.com with SMTP id AL0ETIA2ptwBCsKV for ; Thu, 13 Aug 2009 06:47:19 -0700 (PDT) Message-ID: <4A84195C.8070002@bgs.hu> Date: Thu, 13 Aug 2009 15:47:08 +0200 From: Bgs MIME-Version: 1.0 Subject: Re: fs change on read-only mount References: <4A84090A.6040601@bgs.hu> <20090813131407.GA1088@infradead.org> In-Reply-To: <20090813131407.GA1088@infradead.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 Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Christoph Hellwig Cc: SGI Project XFS mailing list Thanks for the fast answer. So the following scenarios should be ok: 1) Normal boot (no crash, previous mount was ro as well, journal empty) -> mount ro from the beginning => partition hash stays the same 2) Mount rw at any point -> make changes -> remount ro -> sync -> create new hash -> next boot with ro mount has this new hash. Regards Bgs Christoph Hellwig wrote: > On Thu, Aug 13, 2009 at 02:37:30PM +0200, Bgs wrote: >> Greetings, >> >> I don't know xfs' superblock handling well enough, so I'm asking for >> advice here: >> >> Does xfs write anything on the disk when mounting read-only? Is it >> possible to use a partitions hash (or some well defined portion of the >> partition) for integrity checks? > > It should not write anything to disk [1], but older versions did so due to > bugs. Doing a hash of a read-only filesystem should be fine. > >> The partitions are used read-only and hash would be re-generated if any >> rw action was done (after remount ro or full reboot of course). Can this >> be done? I'm concerned about 'mount count' like writes... > > There is no mount-count like write in XFS. > > [1] the only exception is that log reocvery is performed when we attempt > a read-only mount with an unclean log, that is the box crashed while > writing the filesystems. To make sure you never do this always mark > the underlying device readonly, using blkdev --ro. > _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs