[PATCH v4 5/5] selftests/mm: check after-split folio orders in split_huge_page_test.

[Zi Yan <ziy@nvidia.com>]

Instead of just checking the existence of PMD folios before and after folio
split tests, use check_folio_orders() to check after-split folio orders.

The split ranges in split_thp_in_pagecache_to_order_at() are changed to
[addr, addr + pagesize) for every pmd_pagesize. It prevents folios within
the range being split multiple times due to debugfs split function always
perform splits with a pagesize step for a given range.

The following tests are not changed:
1. split_pte_mapped_thp: the test already uses kpageflags to check;
2. split_file_backed_thp: no vaddr available.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 .../selftests/mm/split_huge_page_test.c       | 91 ++++++++++++++-----
 1 file changed, 66 insertions(+), 25 deletions(-)

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index d2467072e752..7d898c380236 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -26,6 +26,7 @@ uint64_t pagesize;
 unsigned int pageshift;
 uint64_t pmd_pagesize;
 unsigned int pmd_order;
+int *expected_orders;
 
 #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
 #define SMAP_PATH "/proc/self/smaps"
@@ -37,6 +38,11 @@ unsigned int pmd_order;
 
 #define GET_ORDER(nr_pages)    (31 - __builtin_clz(nr_pages))
 
+const char *pagemap_proc = "/proc/self/pagemap";
+const char *kpageflags_proc = "/proc/kpageflags";
+int pagemap_fd;
+int kpageflags_fd;
+
 static int is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
 		int kpageflags_fd)
 {
@@ -135,7 +141,8 @@ static int get_page_flags(char *vaddr, int pagemap_fd, int kpageflags_fd,
  * be recorded. Non-present vaddr is skipped.
  *
  * NOTE: the function is used to check folio orders after a split is performed,
- * so it assumes [vaddr_start, len) fully maps to folios within that range.
+ * so it assumes [vaddr_start, len) fully maps to after-split folios within that
+ * range.
  *
  * Return: 0 - no error, -1 - unhandled cases
  */
@@ -369,6 +376,13 @@ static void split_pmd_thp_to_order(int order)
 		if (one_page[i] != (char)i)
 			ksft_exit_fail_msg("%ld byte corrupted\n", i);
 
+	memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+	expected_orders[order] = 4 << (pmd_order - order);
+
+	if (check_after_split_folio_orders(one_page, len, pagemap_fd,
+					   kpageflags_fd, expected_orders,
+					   (pmd_order + 1)))
+		ksft_exit_fail_msg("Unexpected THP split\n");
 
 	if (!check_huge_anon(one_page, 0, pmd_pagesize))
 		ksft_exit_fail_msg("Still AnonHugePages not split\n");
@@ -383,22 +397,6 @@ static void split_pte_mapped_thp(void)
 	size_t len = 4 * pmd_pagesize;
 	uint64_t thp_size;
 	size_t i;
-	const char *pagemap_template = "/proc/%d/pagemap";
-	const char *kpageflags_proc = "/proc/kpageflags";
-	char pagemap_proc[255];
-	int pagemap_fd;
-	int kpageflags_fd;
-
-	if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0)
-		ksft_exit_fail_msg("get pagemap proc error: %s\n", strerror(errno));
-
-	pagemap_fd = open(pagemap_proc, O_RDONLY);
-	if (pagemap_fd == -1)
-		ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
-
-	kpageflags_fd = open(kpageflags_proc, O_RDONLY);
-	if (kpageflags_fd == -1)
-		ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
 
 	one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
 			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
@@ -456,8 +454,6 @@ static void split_pte_mapped_thp(void)
 
 	ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
 	munmap(one_page, len);
-	close(pagemap_fd);
-	close(kpageflags_fd);
 }
 
 static void split_file_backed_thp(int order)
@@ -660,6 +656,7 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
 		const char *fs_loc, int order, int offset)
 {
 	int fd;
+	char *split_addr;
 	char *addr;
 	size_t i;
 	char testfile[INPUT_MAX];
@@ -673,14 +670,33 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
 	err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
 	if (err)
 		return;
+
 	err = 0;
 
-	if (offset == -1)
-		write_debugfs(PID_FMT, getpid(), (uint64_t)addr,
-			      (uint64_t)addr + fd_size, order);
-	else
-		write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)addr,
-			      (uint64_t)addr + fd_size, order, offset);
+	memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+	/*
+	 * use [split_addr, split_addr + pagesize) range to split THPs, since
+	 * the debugfs function always split a range with pagesize step and
+	 * providing a full [addr, addr + fd_size) range can trigger multiple
+	 * splits, complicating after-split result checking.
+	 */
+	if (offset == -1) {
+		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
+			write_debugfs(PID_FMT, getpid(), (uint64_t)split_addr,
+				      (uint64_t)split_addr + pagesize, order);
+
+		expected_orders[order] = fd_size / (pagesize << order);
+	} else {
+		int times = fd_size / pmd_pagesize;
+
+		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
+			write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)split_addr,
+				      (uint64_t)split_addr + pagesize, order, offset);
+
+		for (i = order + 1; i < pmd_order; i++)
+			expected_orders[i] = times;
+		expected_orders[order] = 2 * times;
+	}
 
 	for (i = 0; i < fd_size; i++)
 		if (*(addr + i) != (char)i) {
@@ -689,6 +705,14 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
 			goto out;
 		}
 
+	if (check_after_split_folio_orders(addr, fd_size, pagemap_fd,
+					   kpageflags_fd, expected_orders,
+					   (pmd_order + 1))) {
+		ksft_print_msg("Unexpected THP split\n");
+		err = 1;
+		goto out;
+	}
+
 	if (!check_huge_file(addr, 0, pmd_pagesize)) {
 		ksft_print_msg("Still FilePmdMapped not split\n");
 		err = EXIT_FAILURE;
@@ -740,9 +764,22 @@ int main(int argc, char **argv)
 
 	nr_pages = pmd_pagesize / pagesize;
 	pmd_order = GET_ORDER(nr_pages);
+
+	expected_orders = (int *)malloc(sizeof(int) * (pmd_order + 1));
+	if (!expected_orders)
+		ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
+
 	tests = 2 + (pmd_order - 1) + (2 * pmd_order) + (pmd_order - 1) * 4 + 2;
 	ksft_set_plan(tests);
 
+	pagemap_fd = open(pagemap_proc, O_RDONLY);
+	if (pagemap_fd == -1)
+		ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
+
+	kpageflags_fd = open(kpageflags_proc, O_RDONLY);
+	if (kpageflags_fd == -1)
+		ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
+
 	fd_size = 2 * pmd_pagesize;
 
 	split_pmd_zero_pages();
@@ -767,6 +804,10 @@ int main(int argc, char **argv)
 			split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, offset);
 	cleanup_thp_fs(fs_loc, created_tmp);
 
+	close(pagemap_fd);
+	close(kpageflags_fd);
+	free(expected_orders);
+
 	ksft_finished();
 
 	return 0;
-- 
2.50.1