From: Camille Moncelier Subject: Re: [ext3] Changes to block device after an ext3 mount point has been remounted readonly Date: Tue, 23 Feb 2010 09:42:39 +0100 Message-ID: References: <9F53CAF8-B6B4-40EB-89FA-CD6779D17DBE@sun.com> <20100222223252.GA13882@atrey.karlin.mff.cuni.cz> <20100222230552.GB13882@atrey.karlin.mff.cuni.cz> <16F918FB-F45D-478E-9358-550BB39E277E@sun.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: linux-fsdevel@vger.kernel.org, ext4 development Return-path: Received: from mail-fx0-f219.google.com ([209.85.220.219]:54981 "EHLO mail-fx0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223Ab0BWInB convert rfc822-to-8bit (ORCPT ); Tue, 23 Feb 2010 03:43:01 -0500 In-Reply-To: <16F918FB-F45D-478E-9358-550BB39E277E@sun.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: The fact is that I've been able to reproduce the problem on LVM block devices, and sd* block devices so it's definitely not a loop device specific problem. By the way, I tried several other things other than "echo s >/proc/sysrq_trigger" I tried multiple sync followed with a one minute "sleep", "echo 3 >/proc/sys/vm/drop_caches" seems to lower the chances of "hash changes" but doesn't stops them. On Tue, Feb 23, 2010 at 12:09 AM, Andreas Dilger wrot= e: > On 2010-02-22, at 16:05, Jan Kara wrote: >> >> =A0Hmm, and apparently there is some subtlety in the loopback device= code >> because even when I use sync(1), the first and second images sometim= es >> differ (although it's much rarer). But I see a commit block of the >> transaction =A0already in the first image (the commit block is writt= en last) >> but the contents of the transaction is present only in the second im= age. > > > It has never been safe to run ext3 on top of a loop device, because t= he loop > device does not preserve ordering, and I'm not sure whether it proper= ly > passes barriers either. > > Cheers, Andreas > -- > Andreas Dilger > Sr. Staff Engineer, Lustre Group > Sun Microsystems of Canada, Inc. > > --=20 Camille Moncelier http://devlife.org/ If Java had true garbage collection, most programs would delete themselves upon execution. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html