[PATCH v8 3/4] kselftest: mm: integrate huge page checks

[Yeoreum Yun <yeoreum.yun@arm.com>]

check_large_folios() only checks for large folios without distinguishing
between anonymous and file-backed huge pages.

To add huge page type checking, integrate the huge page checks into
__check_huge():

  1. If hpage_size == pmd_pagesize, check PAGE_IS_HUGE instead of using
     check_large_folios(), since only the mapping type matters. This
     identifies PMD-mapped huge pages.

  2. Otherwise, use check_large_folios() to detect large folios. This
     covers mTHP cases.

  3. Check the folio flags according to the huge page type.

Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Suggested-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 tools/testing/selftests/mm/vm_util.c | 90 +++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 42 deletions(-)

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 969d7202500c..7d23038af1df 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -351,13 +351,13 @@ char *__get_smap_entry(void *addr, const char *pattern, char *buf, size_t len)
 	return entry;
 }
 
-static bool check_large_folios(void *addr, size_t len, int nr_hpages,
+static bool check_large_folios(int pagemap_fd, int kpageflags_fd,
+		void *addr, size_t len, int nr_hpages,
 		uint64_t hpage_size)
 {
 	int order = 0, pagesize = getpagesize();
 	unsigned int nr_pages = hpage_size / pagesize;
 	int orders[MAX_NR_ORDERS], status;
-	int pagemap_fd, kpageflags_fd;
 	bool ret = false;
 
 	if (!nr_pages)
@@ -368,15 +368,6 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages,
 		ksft_exit_fail_msg("invalid order\n");
 
 	memset(orders, 0, sizeof(int) * MAX_NR_ORDERS);
-	pagemap_fd = open(PAGEMAP_PATH, O_RDONLY);
-	if (pagemap_fd == -1)
-		ksft_exit_fail_msg("read pagemap fail\n");
-
-	kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY);
-	if (kpageflags_fd == -1) {
-		close(pagemap_fd);
-		ksft_exit_fail_msg("read kpageflags fail\n");
-	}
 
 	status = gather_folio_orders(addr, len, pagemap_fd,
 			kpageflags_fd, orders, MAX_NR_ORDERS);
@@ -387,8 +378,6 @@ static bool check_large_folios(void *addr, size_t len, int nr_hpages,
 		ret = true;
 
 out:
-	close(pagemap_fd);
-	close(kpageflags_fd);
 	return ret;
 }
 
@@ -411,57 +400,74 @@ static bool check_huge_type(uint64_t categories, enum check_huge_type type)
 	return false;
 }
 
-static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages,
-		  uint64_t hpage_size, enum check_huge_type type)
+static bool __check_huge(void *addr, size_t len, int nr_hpages,
+		uint64_t hpage_size, enum check_huge_type type)
 {
-	int pagemap_fd;
+	bool ret = false;
+	int pagemap_fd, kpageflags_fd;
 	int nr_pmd_mappings = 0;
+	uint64_t pmd_pagesize, scan_mapping_size;
 	uint64_t categories;
+	unsigned long pfn;
+	bool check_pmd_mapping, allow_nonpresent;
 	char *start = addr;
 	char *end = start + len;
 
+	pmd_pagesize = read_pmd_pagesize();
+	if (!pmd_pagesize)
+		ksft_exit_fail_msg("reading PMD pagesize failed\n");
+
+	check_pmd_mapping = hpage_size == pmd_pagesize;
+	scan_mapping_size = (nr_hpages > 0) ? hpage_size : psize();
+	/* Some mTHP tests check a partially populated PMD-sized range. */
+	allow_nonpresent = (uint64_t)nr_hpages * hpage_size < len;
+
 	pagemap_fd = open(PAGEMAP_PATH, O_RDONLY);
 	if (pagemap_fd < 0)
 		ksft_exit_fail_msg("open pagemap fail\n");
 
-	for (; start < end; start += hpage_size) {
+	kpageflags_fd = open(KPAGEFLAGS_PATH, O_RDONLY);
+	if (kpageflags_fd < 0)
+		ksft_exit_fail_msg("open kpageflags fail\n");
+
+	if (!check_pmd_mapping &&
+	    !check_large_folios(pagemap_fd, kpageflags_fd,
+				addr, len, nr_hpages, hpage_size))
+		goto out;
+
+	for (; start < end; start += scan_mapping_size) {
 		categories = pagemap_scan_get_categories(pagemap_fd, start);
-		if (!(categories & PAGE_IS_HUGE))
-			continue;
-		if (check_huge_type(categories, type))
+		pfn = pagemap_get_pfn(pagemap_fd, start);
+		if (pfn == -1UL) {
+			if (!allow_nonpresent)
+				goto out;
+			else
+				continue;
+		}
+		if (check_pmd_mapping && (categories & PAGE_IS_HUGE))
 			nr_pmd_mappings++;
+		if (!check_huge_type(categories, type))
+			goto out;
 	}
-	close(pagemap_fd);
 
-	return nr_hpages == nr_pmd_mappings;
+	if (check_pmd_mapping && (nr_pmd_mappings != nr_hpages))
+		goto out;
+	ret = true;
+
+out:
+	close(pagemap_fd);
+	close(kpageflags_fd);
+	return ret;
 }
 
 bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
 {
-	uint64_t pmd_pagesize = read_pmd_pagesize();
-
-	if (!pmd_pagesize)
-		ksft_exit_fail_msg("reading PMD pagesize failed\n");
-
-	if (hpage_size == pmd_pagesize)
-		return __check_pmd_huge(addr, len, nr_hpages, hpage_size,
-					CHECK_HUGE_ANON);
-
-	return check_large_folios(addr, len, nr_hpages, hpage_size);
+	return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON);
 }
 
 bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
 {
-	uint64_t pmd_pagesize = read_pmd_pagesize();
-
-	if (!pmd_pagesize)
-		ksft_exit_fail_msg("reading PMD pagesize failed\n");
-
-	if (hpage_size == pmd_pagesize)
-		return __check_pmd_huge(addr, len, nr_hpages, hpage_size,
-					CHECK_HUGE_FILE);
-
-	return check_large_folios(addr, len, nr_hpages, hpage_size);
+	return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE);
 }
 
 bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)

-- 
2.43.0