Please provide the rule from /etc/udev/rules.d/64-device-mapper.rules: KERNEL=="device-mapper", NAME="mapper/control"
Please explain further: The /dev/mapper directory is not yet managed by udev, and can't be until the lvm2/dm/udev integration work (that Kay is working on) is complete.
/dev/mapper/control is controlled by udev, IIRC. But if integration work is already on the way, I will close this bug and leave the rule in udev.
It's also controlled by libdevmapper in the sense that if it doesn't exist or any of its properties are incorrect libdevmapper will (re)create it. When the upstream integration work is complete, libdevmapper will no longer change any /dev entries.