[PATCH v2 4/4] userfaultfd: selftest: Cope if shmem doesn't support zeropage

[Thiago Jung Bauermann]

If userfaultfd runs on a system that doesn't support UFFDIO_ZEROPAGE for
shared memory, it currently ends with error code 1 which indicates test
failure:

  # ./userfaultfd shmem 10 10
  nr_pages: 160, nr_pages_per_cpu: 80
  bounces: 9, mode: rnd poll, unexpected missing ioctl for anon memory
  # echo $?
  1

Change userfaultfd_zeropage_test() to return KSFT_SKIP to indicate that
the test is being skipped.

Also change userfaultfd_events_test() and userfaultfd_stress() to ignore
the missing UFFDIO_ZEROPAGE bit from the list of supported ioctls since
these tests don't require that feature.

Signed-off-by: Thiago Jung Bauermann <bauer...@linux.ibm.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 36 +++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c 
b/tools/testing/selftests/vm/userfaultfd.c
index c84e44ddf314..00f1ca663d67 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -852,6 +852,16 @@ static int uffdio_zeropage(int ufd, unsigned long offset)
        return __uffdio_zeropage(ufd, offset, false);
 }
 
+/* Tells whether the kernel doesn't support ZEROPAGE on shared memory VMAs. */
+static bool shmem_without_zeropage_support(unsigned long expected_ioctls,
+                                          unsigned long supported_ioctls)
+{
+       /* Turn off ZEROPAGE bit from expected_ioctls. */
+       expected_ioctls &= ~(1 << _UFFDIO_ZEROPAGE);
+
+       return test_type == TEST_SHMEM && supported_ioctls == expected_ioctls;
+}
+
 /* exercise UFFDIO_ZEROPAGE */
 static int userfaultfd_zeropage_test(void)
 {
@@ -877,10 +887,20 @@ static int userfaultfd_zeropage_test(void)
 
        expected_ioctls = uffd_test_ops->expected_ioctls;
        if ((uffdio_register.ioctls & expected_ioctls) !=
-           expected_ioctls)
+           expected_ioctls) {
+               close(uffd);
+
+               if (shmem_without_zeropage_support(expected_ioctls,
+                                                  uffdio_register.ioctls)) {
+                       fprintf(stderr,
+                               "UFFDIO_ZEROPAGE unsupported in shmem VMAs\n");
+                       return KSFT_SKIP;
+               }
+
                fprintf(stderr,
-                       "unexpected missing ioctl for anon memory\n"),
-                       exit(1);
+                       "unexpected missing ioctl for anon memory\n");
+               return 1;
+       }
 
        if (uffdio_zeropage(uffd, 0)) {
                if (my_bcmp(area_dst, zeropage, page_size))
@@ -924,7 +944,10 @@ static int userfaultfd_events_test(void)
 
        expected_ioctls = uffd_test_ops->expected_ioctls;
        if ((uffdio_register.ioctls & expected_ioctls) !=
-           expected_ioctls)
+           expected_ioctls &&
+           /* No need for zeropage support in this test, so ignore it. */
+           !shmem_without_zeropage_support(expected_ioctls,
+                                           uffdio_register.ioctls))
                fprintf(stderr,
                        "unexpected missing ioctl for anon memory\n"),
                        exit(1);
@@ -1117,7 +1140,10 @@ static int userfaultfd_stress(void)
                }
                expected_ioctls = uffd_test_ops->expected_ioctls;
                if ((uffdio_register.ioctls & expected_ioctls) !=
-                   expected_ioctls) {
+                   expected_ioctls &&
+                   /* No need for zeropage support in this test, so ignore it. 
*/
+                   !shmem_without_zeropage_support(expected_ioctls,
+                                                   uffdio_register.ioctls)) {
                        fprintf(stderr,
                                "unexpected missing ioctl for anon memory\n");
                        return 1;