userfaultfd: hugetlbfs: add userfaultfd_hugetlb test

userfaultfd: hugetlbfs: add userfaultfd_hugetlb test

Orabug: 21685254

Test userfaultfd hugetlb functionality by using the existing testing
method (in userfaultfd.c).  Instead of an anonymous memeory, a hugetlbfs
file is mmap'ed private.  In this way fallocate hole punch can be used to
release pages.  This is because madvise(MADV_DONTNEED) is not supported
for huge pages.

Use the same file, but create wrappers for allocating ranges and releasing
pages.  Compile userfaultfd.c with HUGETLB_TEST defined to produce an
executable to test userfaultfd hugetlb functionality.

Link: http://lkml.kernel.org/r/20161216144821.5183-23-aarcange@redhat.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from linux-next next-20170117
 commit 44d5f4b70ff826f43791aa0fc18ca8fd02f1b432)
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Dhaval Giani <dhaval.giani@oracle.com>
Conflicts:
	tools/testing/selftests/vm/Makefile
	tools/testing/selftests/vm/run_vmtests

Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>