This is new patchset for the shared exception store. You can find the first submission: https://www.redhat.com/archives/dm-devel/2008-August/msg00003.html Seems that there is a chance that the shared exception store feature might be merged into mainline if it's implemented nicely so this time I try to integrate the feature into the existing code more cleanly and submit patches in a reasonable way. There are 10 patches and #1-7 patches include the changes to the existing code necessary to support the shared exception dm-snapshot. My main focus is still a way to incorporate this new feature into the exisiting code nicely. The patches are available (against the latest git tree): http://www.kernel.org/pub/linux/kernel/people/tomo/dm-snap/ If you like a git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tomo/linux-2.6-misc.git dm-snap = In this example, /dev/sda1 is used as an origin device and /dev/sdb1 is used as a cow device. - first, set up an origin and a cow: vine:/home/fujita# echo |dmesg create --notable work vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap-origin /dev/sda1 /dev/sdb1 S 16|dmsetup load work vine:/home/fujita# dmsetup resume work - confirm the current status: vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin : no snapshot - create one snapshot (the id is 0): vine:/home/fujita# dmsetup message work 0 snapshot create 0 - see if the snapshot is created: vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 1 0 - create one more snapshot (the id is 5) and see the result: vine:/home/fujita# dmsetup message work 0 snapshot create 5 vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 2 0 5 Note that creating a snapshot just means that you store some information on the cow device. You don't create a device for it yet. - create a device to access to the snapshot #5 vine:/home/fujita# echo |dmsetup create --notable snap5 vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap /dev/sda1 5|dmsetup load snap5 vine:/home/fujita# dmsetup resume snap5 - confirm the current status: vine:/home/fujita# dmsetup status snap5: 0 268430022 s-snap Unknown work: 0 268430022 s-snap-origin 2 0 5 - remove the devices after you play with them: vine:/home/fujita# dmsetup remove snap5 vine:/home/fujita# dmsetup remove work vine:/home/fujita# dmsetup info No devices found - Again, setup the origin and the cow: vine:/home/fujita# echo |dmsetup create --notable work vine:/home/fujita# echo 0 `blockdev --getsize /dev/sda1` s-snap-origin /dev/sda1 /dev/sdb1 S 16|dmsetup load work vine:/home/fujita# dmsetup resume work vine:/home/fujita# dmsetup status work: 0 268430022 s-snap-origin 2 0 5 Note that you have two snapshots that you created. You can play with them again after creating devices for them. *) By default, dmsetup perfomrs multiple tasks. I uses dmsetup commands that issue a single ioctl to make things clear. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
