+ kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch added to mm-new branch

+ kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch added to mm-new branch

[Andrew Morton]

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The patch titled
     Subject: kselftest: mm: replace usage of /proc/self/smaps for __check_pmd_huge()
has been added to the -mm mm-new branch.  Its filename is
     kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Yeoreum Yun <yeoreum.yun@arm.com>
Subject: kselftest: mm: replace usage of /proc/self/smaps for __check_pmd_huge()
Date: Thu, 24 Sep 2026 20:11:17 +0100

Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on
AArch64”), glibc may call madvise(MADV_HUGEPAGE) for sufficiently large
allocations made by memalign().

The underlying VMA may start at a different address from the aligned
address returned by memalign().  Furthermore, a subsequent
madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is
already set.

This causes split_huge_page_test to fail because the check_pmd_huge()
helpers incorrectly require the address returned by memalign() to match
the VMA start address reported in /proc/self/smaps.

Instead of relying on /proc/self/smaps, use /proc/self/pagemap and
/proc/kpageflags to detect huge-page mappings checking PAGE_IS_HUGE and
PAGE_IS_FILE accroding to type of huge page.

Since shmem pages are also file-backed, simply check whether the page is
file-backed.

Link: https://lore.kernel.org/20260924-fix_split-v8-2-cba7359d882a@arm.com
Fixes: 642bc52aed9 ("selftests: vm: bring common functions to a new file")
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
---

 tools/testing/selftests/mm/vm_util.c |   78 +++++++++++++++----------
 1 file changed, 49 insertions(+), 29 deletions(-)

--- a/tools/testing/selftests/mm/vm_util.c~kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge
+++ a/tools/testing/selftests/mm/vm_util.c
@@ -351,24 +351,6 @@ err_out:
 	return entry;
 }
 
-static bool __check_pmd_huge(void *addr, char *pattern, int nr_hpages,
-		  uint64_t hpage_size)
-{
-	char buffer[MAX_LINE_LENGTH];
-	uint64_t thp = -1;
-	char *entry;
-
-	entry = __get_smap_entry(addr, pattern, buffer, sizeof(buffer));
-	if (!entry)
-		goto err_out;
-
-	if (sscanf(entry, "%9" SCNu64 " kB", &thp) != 1)
-		ksft_exit_fail_msg("Reading smap error\n");
-
-err_out:
-	return thp == (nr_hpages * (hpage_size >> 10));
-}
-
 static bool check_large_folios(void *addr, size_t len, int nr_hpages,
 		uint64_t hpage_size)
 {
@@ -410,20 +392,51 @@ out:
 	return ret;
 }
 
-bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
+enum check_huge_type {
+	CHECK_HUGE_ANON,
+	CHECK_HUGE_FILE,
+};
+
+static bool check_huge_type(uint64_t categories, enum check_huge_type type)
 {
-	uint64_t pmd_pagesize = read_pmd_pagesize();
+	const bool file = categories & PAGE_IS_FILE;
 
-	if (!pmd_pagesize)
-		ksft_exit_fail_msg("reading PMD pagesize failed\n");
+	switch (type) {
+	case CHECK_HUGE_ANON:
+		return !file;
+	case CHECK_HUGE_FILE:
+		return file;
+	}
 
-	if (hpage_size == pmd_pagesize)
-		return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size);
+	return false;
+}
 
-	return check_large_folios(addr, len, nr_hpages, hpage_size);
+static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages,
+		  uint64_t hpage_size, enum check_huge_type type)
+{
+	int pagemap_fd;
+	int nr_pmd_mappings = 0;
+	uint64_t categories;
+	char *start = addr;
+	char *end = start + 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) {
+		categories = pagemap_scan_get_categories(pagemap_fd, start);
+		if (!(categories & PAGE_IS_HUGE))
+			continue;
+		if (check_huge_type(categories, type))
+			nr_pmd_mappings++;
+	}
+	close(pagemap_fd);
+
+	return nr_hpages == nr_pmd_mappings;
 }
 
-bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
+bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
 {
 	uint64_t pmd_pagesize = read_pmd_pagesize();
 
@@ -431,12 +444,13 @@ bool check_huge_file(void *addr, size_t
 		ksft_exit_fail_msg("reading PMD pagesize failed\n");
 
 	if (hpage_size == pmd_pagesize)
-		return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size);
+		return __check_pmd_huge(addr, len, nr_hpages, hpage_size,
+					CHECK_HUGE_ANON);
 
 	return check_large_folios(addr, len, nr_hpages, hpage_size);
 }
 
-bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
+bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
 {
 	uint64_t pmd_pagesize = read_pmd_pagesize();
 
@@ -444,11 +458,17 @@ bool check_huge_shmem(void *addr, size_t
 		ksft_exit_fail_msg("reading PMD pagesize failed\n");
 
 	if (hpage_size == pmd_pagesize)
-		return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size);
+		return __check_pmd_huge(addr, len, nr_hpages, hpage_size,
+					CHECK_HUGE_FILE);
 
 	return check_large_folios(addr, len, nr_hpages, hpage_size);
 }
 
+bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpage_size)
+{
+	return check_huge_file(addr, len, nr_hpages, hpage_size);
+}
+
 int64_t allocate_transhuge(void *ptr, int pagemap_fd)
 {
 	uint64_t ent[2];
_

Patches currently in -mm which might be from yeoreum.yun@arm.com are

kselftest-mm-fix-potential-failure-for-merged-vma-in-guard-regions.patch
kselftest-mm-remove-exclusion-of-building-soft-dirty-test-in-arm64.patch
kselftest-mm-return-fail-when-child-test-result-is-fail-in-khugepaged.patch
kselftest-mm-fix-intermittent-failure-khugepaged-test.patch
kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.patch
kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch
kselftest-mm-integrate-huge-page-checks.patch
kselftest-mm-remove-check_huge_shmem.patch