From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Fri, 27 Oct 2006 07:40:41 -0700 (PDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id k9REeQaG011176 for ; Fri, 27 Oct 2006 07:40:28 -0700 Received: from ogre.sisk.pl (ogre.sisk.pl [217.79.144.158]) by cuda.sgi.com (Spam Firewall) with ESMTP id 66D1B4DE20E for ; Fri, 27 Oct 2006 07:38:38 -0700 (PDT) From: "Rafael J. Wysocki" Subject: Re: [PATCH] Freeze bdevs when freezing processes. Date: Fri, 27 Oct 2006 16:37:21 +0200 References: <1161576735.3466.7.camel@nigel.suspend2.net> <200610261111.30486.rjw@sisk.pl> <20061027013802.GQ8394166@melbourne.sgi.com> In-Reply-To: <20061027013802.GQ8394166@melbourne.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200610271637.21863.rjw@sisk.pl> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: David Chinner Cc: Nigel Cunningham , Pavel Machek , Andrew Morton , LKML , xfs@oss.sgi.com On Friday, 27 October 2006 03:38, David Chinner wrote: > On Thu, Oct 26, 2006 at 11:11:29AM +0200, Rafael J. Wysocki wrote: > > On Thursday, 26 October 2006 10:57, David Chinner wrote: > > > On Thu, Oct 26, 2006 at 06:18:29PM +1000, Nigel Cunningham wrote: > > > > As you have them at the moment, the threads seem to be freezing fine. > > > > The issue I've seen in the past related not to threads but to timer > > > > based activity. Admittedly it was 2.6.14 when I last looked at it, but > > > > there used to be a possibility for XFS to submit I/O from a timer when > > > > the threads are frozen but the bdev isn't frozen. Has that changed? > > > > > > I didn't think we've ever done that - periodic or delayed operations > > > are passed off to the kernel threads to execute. A stack trace > > > (if you still have it) would be really help here. > > > > > > Hmmm - we have a couple of per-cpu work queues as well that are > > > used on I/O completion and that can, in some circumstances, > > > trigger new transactions. If we are only flush metadata, then > > > I don't think that any more I/o will be issued, but I could be > > > wrong (maze of twisty passages). > > > > Well, I think this exactly is the problem, because worker_threads run with > > PF_NOFREEZE set (as I've just said in another message). > > Ok, so freezing the filesystem is the only way you can prevent > this as the workqueues are flushed as part of quiescing the filesystem. Yes, I think so. Now at last I know what the problem actually is and why we need the freezing of filesystems, so thanks for helping me understand that. :-) Greetings, Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller