From: Camille Moncelier Subject: Re: [ext3] Changes to block device after an ext3 mount point has been remounted readonly Date: Fri, 19 Feb 2010 08:38:15 +0100 Message-ID: References: <9F53CAF8-B6B4-40EB-89FA-CD6779D17DBE@sun.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Andreas Dilger , ext4 development To: linux-fsdevel@vger.kernel.org Return-path: Received: from mail-ew0-f219.google.com ([209.85.219.219]:52679 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754660Ab0BSHig (ORCPT ); Fri, 19 Feb 2010 02:38:36 -0500 In-Reply-To: <9F53CAF8-B6B4-40EB-89FA-CD6779D17DBE@sun.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Feb 18, 2010 at 10:41 PM, Andreas Dilger wrote: > Are you sure this isn't because e2fsck has been run at boot time and changed > e.g. the "last checked" timestamp in the superblock? > No, I replaced /sbin/init by something which compute the sha1sum of the root partition, display it then call /sbin/init and I can see that the hash has changed after mount -o remount,ro. As little as I understand, I managed to make a diff between two hexdump of small images where changes happened after I created a file and remounted the fs ro and it seems that, the driver didn't wrote changes to the disk until unmount ( The hexdump clearly shows that /lost+found and /test file has been written after the umount ) workaround: Is there some knob in /proc or /sys which can trigger all pending changes to disk ? ( Like /proc/sys/vm/drop_caches but for filesystems ? ) >> This only happen when the rootfs hash been mounted ro, then remounted >> rw to make some changes and remounted ro. >> On the next reboot the hash will change, but only one time. Next >> reboots will not alter the control sum, until of course I remount it >> RW. > > > Cheers, Andreas > -- > Andreas Dilger > Sr. Staff Engineer, Lustre Group > Sun Microsystems of Canada, Inc. > > -- Camille Moncelier http://devlife.org/ If Java had true garbage collection, most programs would delete themselves upon execution.