selftests/mm: check that FORCE_READ() succeeded

Many cow tests rely on FORCE_READ() to populate pages.  Introduce a helper
to make sure that the pages are actually populated, and fail otherwise.

Link: https://lkml.kernel.org/r/20260122170224.4056513-6-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Suggested-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Usama Anjum <Usama.Anjum@arm.com>
Cc: wang lian <lianux.mm@gmail.com>
Cc: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index 83b3563be26b65f450752bde8b3160c3c486625e..d9c69c04b67d8bb61cfb5779a832d1f70a258554 100644 (file)
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -75,6 +75,18 @@ static bool range_is_swapped(void *addr, size_t size)
        return true;
 }
 
+static bool populate_page_checked(char *addr)
+{
+       bool ret;
+
+       FORCE_READ(*addr);
+       ret = pagemap_is_populated(pagemap_fd, addr);
+       if (!ret)
+               ksft_print_msg("Failed to populate page\n");
+
+       return ret;
+}
+
 struct comm_pipes {
        int child_ready[2];
        int parent_ready[2];
@@ -1549,8 +1561,10 @@ static void run_with_zeropage(non_anon_test_fn fn, const char *desc)
        }
 
        /* Read from the page to populate the shared zeropage. */
-       FORCE_READ(*mem);
-       FORCE_READ(*smem);
+       if (!populate_page_checked(mem) || !populate_page_checked(smem)) {
+               log_test_result(KSFT_FAIL);
+               goto munmap;
+       }
 
        fn(mem, smem, pagesize);
 munmap:
@@ -1612,8 +1626,11 @@ static void run_with_huge_zeropage(non_anon_test_fn fn, const char *desc)
         * the first sub-page and test if we get another sub-page populated
         * automatically.
         */
-       FORCE_READ(*mem);
-       FORCE_READ(*smem);
+       if (!populate_page_checked(mem) || !populate_page_checked(smem)) {
+               log_test_result(KSFT_FAIL);
+               goto munmap;
+       }
+
        if (!pagemap_is_populated(pagemap_fd, mem + pagesize) ||
            !pagemap_is_populated(pagemap_fd, smem + pagesize)) {
                ksft_test_result_skip("Did not get THPs populated\n");
@@ -1663,8 +1680,10 @@ static void run_with_memfd(non_anon_test_fn fn, const char *desc)
        }
 
        /* Fault the page in. */
-       FORCE_READ(*mem);
-       FORCE_READ(*smem);
+       if (!populate_page_checked(mem) || !populate_page_checked(smem)) {
+               log_test_result(KSFT_FAIL);
+               goto munmap;
+       }
 
        fn(mem, smem, pagesize);
 munmap:
@@ -1719,8 +1738,10 @@ static void run_with_tmpfile(non_anon_test_fn fn, const char *desc)
        }
 
        /* Fault the page in. */
-       FORCE_READ(*mem);
-       FORCE_READ(*smem);
+       if (!populate_page_checked(mem) || !populate_page_checked(smem)) {
+               log_test_result(KSFT_FAIL);
+               goto munmap;
+       }
 
        fn(mem, smem, pagesize);
 munmap:
@@ -1773,8 +1794,10 @@ static void run_with_memfd_hugetlb(non_anon_test_fn fn, const char *desc,
        }
 
        /* Fault the page in. */
-       FORCE_READ(*mem);
-       FORCE_READ(*smem);
+       if (!populate_page_checked(mem) || !populate_page_checked(smem)) {
+               log_test_result(KSFT_FAIL);
+               goto munmap;
+       }
 
        fn(mem, smem, hugetlbsize);
 munmap: