v4 of the ioctl interface. Note there never was a v2 or a v3 except in an
unofficial EVMS way.
This works correctly with the 64-bit dev_t patches in -mm kernels.
There is now a config option to allow the user to select v1 or v4, it
defaults to v1. dm-ioctl.[hc] just #includes dm-ioctl-v[14].[hc] depending
on the config option.
If you want to use v4 you will have to update your tools
(libdevmapper/lvm). The latest tools at the time of writing are: