dm-ioctl - DM_DEV_REMOVE

• Removes the reference to a device from the interface layer.

• This means it can no longer be referenced by ioctls.

• If nothing else references the device, it will be freed.

• If something does still reference the device, it will stay around until the final reference is released. This allows tools to be lazy about the order in which they remove related devices. This will get tightened up to make it impossible to leave behind unremovable 'orphan' devices once the existing tools have been enhanced to cope with this.