mm: turn off test_uffdio_wp if CONFIG_PTE_MARKER_UFFD_WP is not configured.

If CONFIG_PTE_MARKER_UFFD_WP is disabled, then we turn off three features
in userfaultfd_api (UFFD_FEATURE_WP_HUGETLBFS_SHMEM,
UFFD_FEATURE_WP_UNPOPULATED, and UFFD_FEATURE_WP_ASYNC).

Currently this test always will call uffdio_regsiter with the flag
UFFDIO_REGISTER_MODE_WP. However, the kernel ensures in vma_can_userfault
that if the feature UFFD_FEATURE_WP_HUGETLBFS_SHMEM is disabled, only
allow the VM_UFFD_WP on anonymous vmas, meaning our call to
uffdio_regsiter will fail.

We still want to be able to run the test even if we have
CONFIG_PTE_MARKER_UFFD_WP disabled, so check to see if the feature
UFFD_FEATURE_WP_HUGETLBFS_SHMEM has been turned off in the test and if so,
disable us from calling uffdio_regsiter with the flag
UFFDIO_REGISTER_MODE_WP.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Audra Mitchell <[e-mail]>
Reviewed-by: Peter Xu <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Christian Brauner <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Rafael Aquini <[e-mail]>
Cc: Shaohua Li <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mm/uffd-stress.c

···
 	test_uffdio_wp = test_uffdio_wp &&
 		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
 
+	if (test_type != TEST_ANON && !(features & UFFD_FEATURE_WP_HUGETLBFS_SHMEM))
+		test_uffdio_wp = false;
+
 	close(uffd);
 	uffd = -1;
 }