linux-kernel - [PATCH 26/29] selftests/mm: Workaround no way to detect uffd-minor + wp

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Message-Id: <20230330160833.3107602-1-peterx@redhat.com>
Date:   Thu, 30 Mar 2023 12:08:33 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>, peterx@...hat.com,
        Leonardo Bras Soares Passos <lsoaresp@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH 26/29] selftests/mm: Workaround no way to detect uffd-minor + wp

Userfaultfd minor+wp mode was very recently added.  The test will fail on
the old kernels at ioctl(UFFDIO_CONTINUE) which is misterious.
Unfortunately there's no feature bit to detect for this support.

Add a hack to leverage WP_UNPOPULATED to detect whether that feature
existed, since WP_UNPOPULATED was merged right after minor+wp.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 tools/testing/selftests/mm/uffd-unit-tests.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index 376dfa320b6f..82fd3aaa06c2 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -784,7 +784,13 @@ uffd_test_case_t uffd_tests[] = {
 		.mem_targets = MEM_SHMEM | MEM_HUGETLB,
 		.uffd_feature_required =
 		UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM |
-		UFFD_FEATURE_PAGEFAULT_FLAG_WP,
+		UFFD_FEATURE_PAGEFAULT_FLAG_WP |
+		/*
+		 * HACK: here we leveraged WP_UNPOPULATED to detect whether
+		 * minor mode supports wr-protect.  There's no feature flag
+		 * for it so this is the best we can test against.
+		 */
+		UFFD_FEATURE_WP_UNPOPULATED,
 	},
 	{
 		.name = "minor-collapse",
-- 
2.39.1