selftests/mm: add tests for splitting pmd THPs to all lower orders

Kernel already supports splitting a folio to any lower order. Test it.

[ziy@nvidia.com: no need to test splitting to order-1]
Link: https://lkml.kernel.org/r/DDA202EA-4664-4F50-A7FD-B00CBB7A624B@nvidia.com
Link: https://lkml.kernel.org/r/20250110235028.96824-2-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Alexander Zhu <alexlzhu@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index cd74ea9b129570d32fc49ace8c083cd4e25eb1c4..3f353f3d070fa133c77dd4bc83bcae3dfa91f83d 100644 (file)
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -144,7 +144,7 @@ void split_pmd_zero_pages(void)
        free(one_page);
 }
 
-void split_pmd_thp(void)
+void split_pmd_thp_to_order(int order)
 {
        char *one_page;
        size_t len = 4 * pmd_pagesize;
@@ -164,7 +164,7 @@ void split_pmd_thp(void)
 
        /* split all THPs */
        write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
-               (uint64_t)one_page + len, 0);
+               (uint64_t)one_page + len, order);
 
        for (i = 0; i < len; i++)
                if (one_page[i] != (char)i)
@@ -174,7 +174,7 @@ void split_pmd_thp(void)
        if (!check_huge_anon(one_page, 0, pmd_pagesize))
                ksft_exit_fail_msg("Still AnonHugePages not split\n");
 
-       ksft_test_result_pass("Split huge pages successful\n");
+       ksft_test_result_pass("Split huge pages to order %d successful\n", order);
        free(one_page);
 }
 
@@ -481,7 +481,7 @@ int main(int argc, char **argv)
        if (argc > 1)
                optional_xfs_path = argv[1];
 
-       ksft_set_plan(4+9);
+       ksft_set_plan(1+8+2+9);
 
        pagesize = getpagesize();
        pageshift = ffs(pagesize) - 1;
@@ -492,7 +492,11 @@ int main(int argc, char **argv)
        fd_size = 2 * pmd_pagesize;
 
        split_pmd_zero_pages();
-       split_pmd_thp();
+
+       for (i = 0; i < 9; i++)
+               if (i != 1)
+                       split_pmd_thp_to_order(i);
+
        split_pte_mapped_thp();
        split_file_backed_thp();