Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751803AbWKGXuS (ORCPT ); Tue, 7 Nov 2006 18:50:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753492AbWKGXuR (ORCPT ); Tue, 7 Nov 2006 18:50:17 -0500 Received: from mx1.redhat.com ([66.187.233.31]:52440 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1751803AbWKGXuP (ORCPT ); Tue, 7 Nov 2006 18:50:15 -0500 Date: Tue, 7 Nov 2006 23:49:51 +0000 From: Alasdair G Kergon To: "Rafael J. Wysocki" Cc: Eric Sandeen , Andrew Morton , Alasdair G Kergon , linux-kernel@vger.kernel.org, dm-devel@redhat.com, Ingo Molnar , Srinivasa DS Subject: Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex Message-ID: <20061107234951.GD30653@agk.surrey.redhat.com> Mail-Followup-To: "Rafael J. Wysocki" , Eric Sandeen , Andrew Morton , Alasdair G Kergon , linux-kernel@vger.kernel.org, dm-devel@redhat.com, Ingo Molnar , Srinivasa DS References: <20061107183459.GG6993@agk.surrey.redhat.com> <20061107122837.54828e24.akpm@osdl.org> <45510C73.7060408@redhat.com> <200611080005.50070.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200611080005.50070.rjw@sisk.pl> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1239 Lines: 25 On Wed, Nov 08, 2006 at 12:05:49AM +0100, Rafael J. Wysocki wrote: > But freeze_bdev() is supposed to return the result of get_super(bdev) > _unconditionally_. Moreover, in its current form freeze_bdev() _cannot_ > _fail_, so I don't see how this change doesn't break any existing code. > For example freeze_filesystems() (recently added to -mm) will be broken > if the down_trylock() is unsuccessful. I hadn't noticed that -mm patch. I'll take a look. Up to now, device-mapper (via dmsetup) and xfs (via xfs_freeze, which dates from before device-mapper handled this automatically) were the only users. Only one freeze should be issued at once. A freeze is a temporary thing, normally used while creating a snapshot. (One problem we still have is lots of old documentation on the web advising people to run xfs_freeze before creating device-mapper snapshots.) You're right that the down_trylock idea is more trouble than it's worth and should be scrapped. Alasdair -- agk@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/