From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161209AbWKIUCO (ORCPT ); Thu, 9 Nov 2006 15:02:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161803AbWKIUCN (ORCPT ); Thu, 9 Nov 2006 15:02:13 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:14506 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S1161209AbWKIUCN (ORCPT ); Thu, 9 Nov 2006 15:02:13 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex Date: Thu, 9 Nov 2006 20:59:47 +0100 User-Agent: KMail/1.9.1 Cc: Alasdair G Kergon , Eric Sandeen , Andrew Morton , linux-kernel@vger.kernel.org, dm-devel@redhat.com, Srinivasa DS , Nigel Cunningham , David Chinner References: <20061107183459.GG6993@agk.surrey.redhat.com> <200611091652.34649.rjw@sisk.pl> <20061109160003.GA24156@elf.ucw.cz> In-Reply-To: <20061109160003.GA24156@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200611092059.48722.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thursday, 9 November 2006 17:00, Pavel Machek wrote: > Hi! > > > > > Well, it looks like the interactions with dm add quite a bit of > > > > complexity here. > > > > > > What about just fixing xfs (thou shall not write to disk when kernel > > > threads are frozen), and getting rid of blockdev freezing? > > > > Well, first I must admit you were absolutely right being suspicious with > > respect to this stuff. > > (OTOH your patch found real bugs in suspend.c, so...) > > > OTOH I have no idea _how_ we can tell xfs that the processes have been > > frozen. Should we introduce a global flag for that or something? > > I guess XFS should just do all the writes from process context, and > refuse any writing when its threads are frozen... I actually still > believe it is doing the right thing, because you can't really write to > disk from timer. This is from a work queue, so in fact from a process context, but from a process that is running with PF_NOFREEZE. And I don't think we can forbid filesystems to use work queues. IMO it's a legitimate thing to do for an fs. _But_. Alasdair, do I think correctly that if there's a suspended device-mapper device below an non-frozen filesystem, then sys_sync() would block just as well as freeze_bdev() on this filesystem? Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller