From Bill Irwin

Optionally back priviled processes' shm with hugetlbfs.

One of the more common requests for and/or users of hugetlb interfaces
in general are databases using shm.  This patch exports functionality
mostly equivalent to tmpfs, adds the calling sequence to ipc/shm.c, and
hashes out a small support function in fs/hugetlbfs/inode.c so that shm
segments may be hugetlbpage-backed if userspace passes a flag to
shmget().

Access to this resource requires CAP_IPC_LOCK.