Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753927Ab1DSIfW (ORCPT ); Tue, 19 Apr 2011 04:35:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27787 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752167Ab1DSIfT (ORCPT ); Tue, 19 Apr 2011 04:35:19 -0400 Subject: Re: Linux 2.6.39-rc3 From: Steven Whitehouse To: "Aneesh Kumar K.V" Cc: Kay Sievers , Dave Jones , Linus Torvalds , Linux Kernel Mailing List , Eric Sandeen In-Reply-To: <87ipuar6nq.fsf@linux.vnet.ibm.com> References: <20110412190934.GA12082@redhat.com> <20110412192103.GA13278@redhat.com> <87tye1ckhr.fsf@linux.vnet.ibm.com> <87ipuar6nq.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Organization: Red Hat UK Ltd Date: Tue, 19 Apr 2011 09:37:47 +0100 Message-ID: <1303202267.2702.6.camel@dolmen> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2856 Lines: 69 Hi, On Tue, 2011-04-19 at 13:53 +0530, Aneesh Kumar K.V wrote: > On Tue, 19 Apr 2011 00:57:27 +0200, Kay Sievers wrote: > > On Thu, Apr 14, 2011 at 10:20, Aneesh Kumar K.V > > wrote: > > > On Tue, 12 Apr 2011 15:21:03 -0400, Dave Jones wrote: > > >> On Tue, Apr 12, 2011 at 03:09:34PM -0400, Dave Jones wrote: > > >> > > >> > however, the output of mount looks very confused.. > > >> > > > >> > .38: > > >> > /dev/mapper/vg_adamo-lv_home on /home type ext4 (rw,relatime,seclabel,barrier=1,data=ordered) > > >> > > > >> > .39: > > >> > - on /home type 79a9-4526-888c-1f86d35a6704 (rw,relatime,ext4) > > >> > > > >> > It looks like /proc/self/mountinfo broke abi. > > >> > > > >> > .38: > > >> > 48 45 253:3 / /home rw,relatime - ext4 /dev/mapper/vg_adamo-lv_home rw,seclabel,barrier=1,data=ordered > > >> > > > >> > .39: > > >> > 46 22 253:3 / /home rw,relatime uuid:f3971858-79a9-4526-888c-1f86d35a6704 - ext4 /dev/mapper/vg_adamo-lv_home rw,seclabel,user_xattr,barrier=1,data=ordered > > >> > > >> looks like this was caused by 93f1c20bc8cdb757be50566eff88d65c3b26881f > > >> > > >> perhaps adding that string to the end of the line would preserve what mount expects ? > > > > > > uuid: is the option field as per > > > Documentation/filesystem/proc.txt. There was an error in libmount > > > parsing which got fixed upstream recently > > > > Just a simple question about this approach in general? A filesystem > > UUID can be changed on disk at any time (tune2fs -U ...). > > > > Your code looks like you copy the bytes to the in-kernel superblock > > structure without noticing any later changes on disk? How is that > > supposed to work? > > > > Isn't that true even for the fsid returned by statfs ?. IIUC tune2fs > won't change even the ext4_super_block.s_uuid . > > -aneesh For gfs2 we insist that the volume label (lock table name) and the uuid do not change during the lifetime of a mount since they are used as identifiers by the userland infrastructure. We include them with all uevent messages, for example, and we do not have a "uuid changed" uevent. So we use exactly the behaviour proposed: copying the info from the sb at mount time and then never changing it during the lifetime of the mount. The doesn't prevent someone making an on-disk change though while the fs is mounted with tunegfs2 (or gfs2_tool for older gfs2-utils). One question though, is why would it be useful to change the uuid of a mounted filesystem? It seems likely to lead to confusion for no useful gain, Steve. -- 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/