[PATCH v4 4/7] mm/selftests: Fix split_huge_page_test failure on systems with 64KB page size

[Aboorva Devarajan <aboorvad@linux.ibm.com>]

From: Donet Tom <donettom@linux.ibm.com>

The split_huge_page_test fails on systems with a 64KB base page size.
This is because the order of a 2MB huge page is different:

On 64KB systems, the order is 5.

On 4KB systems, it's 9.

The test currently assumes a maximum huge page order of 9, which is only
valid for 4KB base page systems. On systems with 64KB pages, attempting
to split huge pages beyond their actual order (5) causes the test to fail.

In this patch, we calculate the huge page order based on the system's base
page size. With this change, the tests now run successfully on both 64KB
and 4KB page size systems.

Fixes: fa6c02315f745 ("mm: huge_memory: a new debugfs interface for splitting THP tests")
Co-developed-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
---
 tools/testing/selftests/mm/cow.c              |  5 -----
 .../selftests/mm/split_huge_page_test.c       | 22 ++++++++++++-------
 tools/testing/selftests/mm/uffd-wp-mremap.c   |  5 -----
 tools/testing/selftests/mm/vm_util.h          |  5 +++++
 4 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index 90ee5779662f..e742d9313798 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -41,11 +41,6 @@ static size_t hugetlbsizes[10];
 static int gup_fd;
 static bool has_huge_zeropage;
 
-static int sz2ord(size_t size)
-{
-	return __builtin_ctzll(size / pagesize);
-}
-
 static int detect_thp_sizes(size_t sizes[], int max)
 {
 	int count = 0;
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index eadbeb820d71..7cbeaebc9d71 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -523,6 +523,9 @@ int main(int argc, char **argv)
 	const char *fs_loc;
 	bool created_tmp;
 	int offset;
+	unsigned int max_order;
+	unsigned int nr_pages;
+	unsigned int tests;
 
 	ksft_print_header();
 
@@ -534,35 +537,38 @@ int main(int argc, char **argv)
 	if (argc > 1)
 		optional_xfs_path = argv[1];
 
-	ksft_set_plan(1+8+1+9+9+8*4+2);
-
 	pagesize = getpagesize();
 	pageshift = ffs(pagesize) - 1;
 	pmd_pagesize = read_pmd_pagesize();
 	if (!pmd_pagesize)
 		ksft_exit_fail_msg("Reading PMD pagesize failed\n");
 
+	nr_pages = pmd_pagesize / pagesize;
+	max_order =  sz2ord(pmd_pagesize);
+	tests = 2 + (max_order - 1) + (2 * max_order) + (max_order - 1) * 4 + 2;
+	ksft_set_plan(tests);
+
 	fd_size = 2 * pmd_pagesize;
 
 	split_pmd_zero_pages();
 
-	for (i = 0; i < 9; i++)
+	for (i = 0; i < max_order; i++)
 		if (i != 1)
 			split_pmd_thp_to_order(i);
 
 	split_pte_mapped_thp();
-	for (i = 0; i < 9; i++)
+	for (i = 0; i < max_order; i++)
 		split_file_backed_thp(i);
 
 	created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
 			&fs_loc);
-	for (i = 8; i >= 0; i--)
+	for (i = max_order - 1; i >= 0; i--)
 		split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1);
 
-	for (i = 0; i < 9; i++)
+	for (i = 0; i < max_order; i++)
 		for (offset = 0;
-		     offset < pmd_pagesize / pagesize;
-		     offset += MAX(pmd_pagesize / pagesize / 4, 1 << i))
+		     offset < nr_pages;
+		     offset += MAX(nr_pages / 4, 1 << i))
 			split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, offset);
 	cleanup_thp_fs(fs_loc, created_tmp);
 
diff --git a/tools/testing/selftests/mm/uffd-wp-mremap.c b/tools/testing/selftests/mm/uffd-wp-mremap.c
index 13ceb5628970..7140b2f9c452 100644
--- a/tools/testing/selftests/mm/uffd-wp-mremap.c
+++ b/tools/testing/selftests/mm/uffd-wp-mremap.c
@@ -19,11 +19,6 @@ static size_t thpsizes[20];
 static int nr_hugetlbsizes;
 static size_t hugetlbsizes[10];
 
-static int sz2ord(size_t size)
-{
-	return __builtin_ctzll(size / pagesize);
-}
-
 static int detect_thp_sizes(size_t sizes[], int max)
 {
 	int count = 0;
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 1843ad48d32b..85f7dae9a0c1 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -127,6 +127,11 @@ static inline void log_test_result(int result)
 	ksft_test_result_report(result, "%s\n", test_name);
 }
 
+static inline int sz2ord(size_t size)
+{
+	return __builtin_ctzll(size / getpagesize());
+}
+
 void *sys_mremap(void *old_address, unsigned long old_size,
 		 unsigned long new_size, int flags, void *new_address);
 
-- 
2.47.1