From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Wed, 25 Oct 2006 06:51:24 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id k9PDpCaG004189 for ; Wed, 25 Oct 2006 06:51:13 -0700 Received: from pop5-1.us4.outblaze.com (pop5-1.us4.outblaze.com [205.158.62.125]) by cuda.sgi.com (Spam Firewall) with SMTP id C6568D1AD073 for ; Wed, 25 Oct 2006 06:50:25 -0700 (PDT) Subject: Re: [PATCH] Freeze bdevs when freezing processes. From: Nigel Cunningham In-Reply-To: <200610251432.41958.rjw@sisk.pl> References: <1161576735.3466.7.camel@nigel.suspend2.net> <20061025083830.GI11034@melbourne.sgi.com> <20061025084714.GA7266@elf.ucw.cz> <200610251432.41958.rjw@sisk.pl> Content-Type: text/plain Date: Wed, 25 Oct 2006 23:23:40 +1000 Message-Id: <1161782620.3638.0.camel@nigel.suspend2.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: "Rafael J. Wysocki" Cc: Pavel Machek , David Chinner , Andrew Morton , LKML , xfs@oss.sgi.com Hi. On Wed, 2006-10-25 at 14:32 +0200, Rafael J. Wysocki wrote: > On Wednesday, 25 October 2006 10:47, Pavel Machek wrote: > > On Wed 2006-10-25 18:38:30, David Chinner wrote: > > > On Wed, Oct 25, 2006 at 10:10:01AM +0200, Pavel Machek wrote: > > > > > Hence the only way to correctly rebuild the XFS state on resume is > > > > > to quiesce the filesystem on suspend and thaw it on resume so as to > > > > > trigger log recovery. > > > > > > > > No, during suspend/resume, memory image is saved, and no state is > > > > lost. We would not even have to do sys_sync(), and suspend/resume > > > > would still work properly. > > > > > > It seems to me that you ensure the filesystem is synced to disk and > > > then at some point later you record the memory state of the > > > filesystem, but these happen at different times. That leaves a > > > window for things to get out of sync again, right? > > > > I DO NOT HAVE TO ENSURE FILESYSTEM IS SYNCED. That sys_sync() is > > optional. > > > > Recording of memory state is atomic, and as long as noone writes to > > the disk after atomic snapshot, memory image matches what is on disk. > > Well, my impression is that this is exactly what happens here: Something > in the XFS code causes metadata to be written to disk _after_ the atomic > snapshot. > > That's why I asked if the dirty XFS metadata were flushed by a kernel thread. When I first added bdev freezing it was because there was an XFS timer doing writes. Regards, Nigel