+ selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes.patch added to mm-new branch

The patch titled
     Subject: selftests/mm: add PAGEMAP_SCAN test for THP PMD holes
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes.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: "Kiryl Shutsemau (Meta)" <[email protected]>
Subject: selftests/mm: add PAGEMAP_SCAN test for THP PMD holes
Date: Wed, 15 Jul 2026 15:42:34 +0100

Add coverage for the PMD-hole case fixed by "fs/proc/task_mmu: fix
PAGEMAP_SCAN written state for PMD holes": a MAP_PRIVATE|MAP_ANON THP that
is uffd-wp'd and then dropped with MADV_DONTNEED leaves a pmd_none hole
with no page table, which PAGEMAP_SCAN must still report as written.

Factor the populate/drop/scan-both-paths sequence out of
unpopulated_scan_test() into a helper, and add unpopulated_thp_scan_test()
that reuses it with a THP.

Include <linux/mman.h> for MADV_COLLAPSE; <sys/mman.h> lacks it on older
glibc (e.g. 2.34). Same approach as commit fd5295afae91 ("selftests/mm:
hmm-tests: include linux/mman.h to access MADV_COLLAPSE").

Link: https://lore.kernel.org/aljWYfPRCVc6IB2b@thinkstation
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Kiryl Shutsemau <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Zenghui Yu <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pedro Falcato <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Assisted-by: Claude:claude-fable-5
Signed-off-by: Andrew Morton <[email protected]>
---

 tools/testing/selftests/mm/pagemap_ioctl.c |  102 +++++++++++++------
 1 file changed, 75 insertions(+), 27 deletions(-)

--- a/tools/testing/selftests/mm/pagemap_ioctl.c~selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes
+++ a/tools/testing/selftests/mm/pagemap_ioctl.c
@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <malloc.h>
 #include <linux/types.h>
+#include <linux/mman.h>
 #include <linux/memfd.h>
 #include <linux/userfaultfd.h>
 #include <linux/fs.h>
@@ -1058,50 +1059,96 @@ static void test_simple(void)
  * the generic path (reached e.g. via category_anyof_mask) must report every
  * page written.
  */
-static void unpopulated_scan_test(void)
+/*
+ * Populate @mem (optionally collapsing it into a THP first), drop it with
+ * MADV_DONTNEED, then check PAGEMAP_SCAN reports the whole range written via
+ * both the fast and generic query paths. A dropped THP leaves a pmd_none hole
+ * with no page table, exercising pagemap_scan_pte_hole(); a base-page range
+ * leaves pte_none entries.
+ */
+static void unpopulated_written_test(const char *name, char *mem, long size,
+				     bool use_thp)
 {
-	int npages = 16, i;
-	long mem_size = npages * page_size;
+	long npages = size / page_size, fast = 0, slow = 0, ret;
 	struct page_region regions[16];
-	long fast = 0, slow = 0, ret;
-	char *mem;
-
-	mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE,
-		   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-	if (mem == MAP_FAILED)
-		ksft_exit_fail_msg("%s mmap failed\n", __func__);
+	int i;
 
-	wp_init(mem, mem_size);
+	wp_init(mem, size);
 
-	/* Populate, then drop: the ptes become pte_none without a marker. */
-	memset(mem, 1, mem_size);
-	if (madvise(mem, mem_size, MADV_DONTNEED))
-		ksft_exit_fail_msg("%s MADV_DONTNEED failed\n", __func__);
+	/* Populate, optionally collapse to a THP, then drop it. */
+	memset(mem, 1, size);
+	if (use_thp &&
+	    (madvise(mem, size, MADV_COLLAPSE) ||
+	     !check_huge_anon(mem, size / hpage_size, hpage_size))) {
+		ksft_test_result_skip("%s could not form a THP\n", name);
+		goto out;
+	}
+	if (madvise(mem, size, MADV_DONTNEED)) {
+		ksft_test_result_fail("%s MADV_DONTNEED failed\n", name);
+		goto out;
+	}
 
 	/* Fast path: category_mask == return_mask == PAGE_IS_WRITTEN. */
-	ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0,
+	ret = pagemap_ioctl(mem, size, regions, ARRAY_SIZE(regions), 0, 0,
 			    PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN);
-	if (ret < 0)
-		ksft_exit_fail_msg("%s fast scan failed\n", __func__);
-	for (i = 0; i < ret; i++)
+	for (i = 0; ret > 0 && i < ret; i++)
 		fast += LEN(regions[i]);
 
 	/* Generic path: same query expressed via category_anyof_mask. */
-	ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0,
+	ret = pagemap_ioctl(mem, size, regions, ARRAY_SIZE(regions), 0, 0,
 			    0, PAGE_IS_WRITTEN, 0, PAGE_IS_WRITTEN);
-	if (ret < 0)
-		ksft_exit_fail_msg("%s generic scan failed\n", __func__);
-	for (i = 0; i < ret; i++)
+	for (i = 0; ret > 0 && i < ret; i++)
 		slow += LEN(regions[i]);
 
 	ksft_test_result(fast == npages && slow == npages,
-			 "%s unpopulated ptes reported written by both paths (%ld, %ld of %d)\n",
-			 __func__, fast, slow, npages);
+			 "%s unpopulated range reported written by both paths (%ld, %ld of %ld)\n",
+			 name, fast, slow, npages);
+out:
+	wp_free(mem, size);
+}
 
-	wp_free(mem, mem_size);
+static void unpopulated_scan_test(void)
+{
+	long mem_size = 16 * page_size;
+	char *mem;
+
+	mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE,
+		   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (mem == MAP_FAILED) {
+		ksft_test_result_skip("%s mmap failed\n", __func__);
+		return;
+	}
+
+	unpopulated_written_test(__func__, mem, mem_size, false);
 	munmap(mem, mem_size);
 }
 
+/*
+ * Same as unpopulated_scan_test(), but the range is a THP: a full-PMD
+ * MADV_DONTNEED leaves a pmd_none hole with no page table.
+ */
+static void unpopulated_thp_scan_test(void)
+{
+	char *area, *mem;
+
+	if (!hpage_size) {
+		ksft_test_result_skip("%s THP not supported\n", __func__);
+		return;
+	}
+
+	/* Over-allocate so a PMD-aligned, THP-sized range fits inside. */
+	area = mmap(NULL, 2 * hpage_size, PROT_READ | PROT_WRITE,
+		    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (area == MAP_FAILED) {
+		ksft_test_result_skip("%s mmap failed\n", __func__);
+		return;
+	}
+	mem = (char *)(((unsigned long)area + hpage_size - 1) & ~(hpage_size - 1));
+
+	unpopulated_written_test(__func__, mem, hpage_size, true);
+	munmap(area, 2 * hpage_size);
+}
+
 int sanity_tests(void)
 {
 	unsigned long long mem_size, vec_size;
@@ -1610,7 +1657,7 @@ int main(int __attribute__((unused)) arg
 	if (!hugetlb_setup_default(4))
 		ksft_print_msg("HugeTLB test will be skipped\n");
 
-	ksft_set_plan(118);
+	ksft_set_plan(119);
 
 	page_size = getpagesize();
 	hpage_size = read_pmd_pagesize();
@@ -1790,6 +1837,7 @@ int main(int __attribute__((unused)) arg
 
 	/* 18. Unpopulated pte scan-path consistency */
 	unpopulated_scan_test();
+	unpopulated_thp_scan_test();
 
 	close(pagemap_fd);
 	ksft_finished();
_

Patches currently in -mm which might be from [email protected] are

fs-proc-task_mmu-fix-pagemap_scan-written-state-for-unpopulated-ptes.patch
mm-hugetlb-fix-swap-entry-corruption-when-clearing-uffd-wp-at-fork.patch
fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes.patch
mm-decouple-protnone-helpers-from-config_numa_balancing.patch
mm-rename-uffd-wp-pte-bit-macros-to-uffd.patch
mm-rename-uffd-wp-pte-accessors-to-uffd.patch
userfaultfd-test-uffd-vma-flags-through-the-vma_flags_t-api.patch
mm-add-vm_uffd_rwp-vma-flag.patch
mm-add-mm_cp_uffd_rwp-change_protection-flag.patch
mm-preserve-rwp-marker-across-pte-rewrites.patch
mm-handle-vm_uffd_rwp-in-khugepaged-rmap-and-gup.patch
userfaultfd-add-uffdio_register_mode_rwp-and-uffdio_rwprotect-plumbing.patch
mm-userfaultfd-add-rwp-fault-delivery-and-expose-uffdio_register_mode_rwp.patch
mm-pagemap-add-page_is_accessed-for-rwp-tracking.patch
userfaultfd-add-uffd_feature_rwp_async-for-async-fault-resolution.patch
userfaultfd-add-uffdio_set_mode-for-runtime-sync-async-toggle.patch
selftests-mm-add-userfaultfd-rwp-tests.patch
documentation-userfaultfd-document-rwp-working-set-tracking.patch
selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes.patch