selftests/mm: skip uffd hugetlb tests with insufficient hugepages

Now that run_vmtests.sh does not guarantee that the correct hugepage count
is available, add a check inside the userfaultfd hugetlb test to verify
the nr_hugepages count before continuing.

Link: https://lkml.kernel.org/r/20240306223714.320681-3-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: PacheNico

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

@@ -441,6 +441,12 @@ int main(int argc, char **argv)
 	parse_test_type_arg(argv[1]);
 	bytes = atol(argv[2]) * 1024 * 1024;
 
+	if (test_type == TEST_HUGETLB &&
+	   get_free_hugepages() < bytes / page_size) {
+		printf("skip: Skipping userfaultfd... not enough hugepages\n");
+		return KSFT_SKIP;
+	}
+
 	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 
 	nr_pages_per_cpu = bytes / page_size / nr_cpus;