The test requires thp, skip the test when thp is not available to avoid
false positive.

Tested with thp disabled kernel.
Before the fix:
  # --------------------------------
  # running ./transhuge-stress -d 20
  # --------------------------------
  # TAP version 13
  # 1..1
  # transhuge-stress: allocate 1453 transhuge pages, using 2907 MiB virtual memory and 11 MiB of ram
  # Bail out! MADV_HUGEPAGE# Planned tests != run tests (1 != 0)
  # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
  # [FAIL]
  not ok 60 transhuge-stress -d 20 # exit=1

After the fix:
  # --------------------------------
  # running ./transhuge-stress -d 20
  # --------------------------------
  # 1..0 # SKIP Transparent Hugepages not available
  # [SKIP]
  ok 5 transhuge-stress -d 20 # SKIP

CC: Li Wang <liwang@redhat.com>
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
---
 tools/testing/selftests/mm/transhuge-stress.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/mm/transhuge-stress.c b/tools/testing/selftests/mm/transhuge-stress.c
index bcad47c09518..76316696426d 100644
--- a/tools/testing/selftests/mm/transhuge-stress.c
+++ b/tools/testing/selftests/mm/transhuge-stress.c
@@ -17,6 +17,7 @@
 #include <sys/mman.h>
 #include "vm_util.h"
 #include "kselftest.h"
+#include "thp_settings.h"
 
 int backing_fd = -1;
 int mmap_flags = MAP_ANONYMOUS | MAP_NORESERVE | MAP_PRIVATE;
@@ -35,6 +36,9 @@ int main(int argc, char **argv)
 	int pagemap_fd;
 	int duration = 0;
 
+	if (!thp_is_enabled())
+		ksft_exit_skip("Transparent Hugepages not available\n");
+
 	ksft_print_header();
 
 	ram = sysconf(_SC_PHYS_PAGES);
-- 
2.53.0