userfaultfd: hugetlbfs: add userfaultfd_hugetlb test

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/vm/run_vmtests

@@ -103,6 +103,19 @@ else
 	echo "[PASS]"
 fi
 
+echo "----------------------------"
+echo "running userfaultfd_hugetlb"
+echo "----------------------------"
+# 258MB total huge pages == 128MB src and 128MB dst
+./userfaultfd_hugetlb 128 32 $mnt/ufd_test_file
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+	exitcode=1
+else
+	echo "[PASS]"
+fi
+rm -f $mnt/ufd_test_file
+
 #cleanup
 umount $mnt
 rm -rf $mnt