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[49.196.94.140]) by smtp.gmail.com with ESMTPSA id y5-20020aa78045000000b0062606b4ecb3sm3698448pfm.108.2023.03.18.17.17.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Mar 2023 17:17:06 -0700 (PDT) Received: from dave by destitution with local (Exim 4.96) (envelope-from ) id 1pdgjA-000NK4-0J; Sun, 19 Mar 2023 11:16:48 +1100 Date: Sun, 19 Mar 2023 11:16:48 +1100 From: Dave Chinner To: Catherine Hoang Cc: "linux-xfs@vger.kernel.org" Subject: Re: [PATCH v1 0/4] setting uuid of online filesystems Message-ID: References: <20230314042109.82161-1-catherine.hoang@oracle.com> <20230314062847.GQ360264@dread.disaster.area> <953CAB5C-E645-4BB2-88E2-E992C5CC565D@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <953CAB5C-E645-4BB2-88E2-E992C5CC565D@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Mar 16, 2023 at 08:41:14PM +0000, Catherine Hoang wrote: > > On Mar 13, 2023, at 11:28 PM, Dave Chinner wrote: > > > > On Mon, Mar 13, 2023 at 09:21:05PM -0700, Catherine Hoang wrote: > >> Hi all, > >> > >> This series of patches implements a new ioctl to set the uuid of mounted > >> filesystems. Eventually this will be used by the 'xfs_io fsuuid' command > >> to allow userspace to update the uuid. > >> > >> Comments and feedback appreciated! > > > > What's the use case for this? > > We want to be able to change the uuid on newly mounted clone vm images > so that each deployed system has a different uuid. We need to do this the > first time the system boots, but after the root fs is mounted so that fsuuid > can run in parallel with other service startup to minimize deployment times. Why can't you do it offline immediately after the offline clone of the golden image? I mean, cloning images and setting up their contents is something the external orchestration software does and will always have to do, so i don't really understand why UUID needs to be modified at first mount vs at clone time. Can you describe why it actually needs to be done after first mount? > >> xfs: add XFS_IOC_SETFSUUID ioctl > >> xfs: export meta uuid via xfs_fsop_geom > > > > For what purpose does userspace ever need to know the sb_meta_uuid? > > Userspace would need to know the meta uuid if we want to restore > the original uuid after it has been changed. I don't understand why you'd want to restore the original UUID given the use case you've describe. Can you explain the situation where you want to return a cloned image to the original golden image UUID? -Dave. -- Dave Chinner david@fromorbit.com