Lvm2 has been extended with support for creation of thin snapshot of some existing non-thinly-provisioned LV.
Thin-pool can be now used for snapshots of non-thin volumes with all the performance gains from thin pool target compared with traditional snapshot target.
Result (if any):
Original read-only inactive non-thinly-provisioned volume is converted into external origin for thin snapshot volume and stays unmodified and could be even used for multiple snapshots. Thin volume could be than used for any further modification of device instead.
Note: current lvm2 version doesn't support merge feature, so unlike with older lvm2 snapshots, updated device cannot be merged back into its origin device.