+ testing-selftests-mm-add-soft-dirty-merge-self-test.patch added to mm-new branch

+ testing-selftests-mm-add-soft-dirty-merge-self-test.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: testing/selftests/mm: add soft-dirty merge self-test
has been added to the -mm mm-new branch.  Its filename is
     testing-selftests-mm-add-soft-dirty-merge-self-test.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/testing-selftests-mm-add-soft-dirty-merge-self-test.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.

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Subject: testing/selftests/mm: add soft-dirty merge self-test
Date: Fri, 14 Nov 2025 17:53:19 +0000

Assert that we correctly merge VMAs containing VM_SOFTDIRTY flags now that
we correctly handle these as sticky.

In order to do so, we have to account for the fact the pagemap interface
checks soft dirty PTEs and additionally that newly merged VMAs are marked
VM_SOFTDIRTY.

To account for this we use unfaulted anon VMAs, mapping one VMA in and
clearing soft-dirty, then another separate from the first which will be
marked soft-dirty which we then mremap() into place.

Link: https://lkml.kernel.org/r/0db6aeb73d42876756ba73163cc0cc6e7e8c6100.1763142412.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/soft-dirty.c |   51 +++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/soft-dirty.c~testing-selftests-mm-add-soft-dirty-merge-self-test
+++ a/tools/testing/selftests/mm/soft-dirty.c
@@ -184,6 +184,54 @@ static void test_mprotect(int pagemap_fd
 		close(test_fd);
 }
 
+static void test_merge(int pagemap_fd, int pagesize)
+{
+	char *reserved, *map, *map2;
+
+	/* Reserve space. */
+	reserved = mmap(NULL, 4 * pagesize, PROT_NONE,
+			MAP_ANON | MAP_PRIVATE, -1, 0);
+	if (reserved == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+	munmap(reserved, 4 * pagesize);
+
+	/* Map a page. */
+	map = mmap(&reserved[pagesize], pagesize, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/* This will clear VM_SOFTDIRTY too. */
+	clear_softdirty();
+
+	/*
+	 * Now place a new mapping which will be marked VM_SOFTDIRTY. Away from
+	 * map.
+	 */
+	map2 = mmap(&reserved[3 * pagesize], pagesize, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	if (map2 == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed\n");
+
+	/*
+	 * Now remap it immediately adjacent to map, if the merge correctly
+	 * propagates VM_SOFTDIRTY, we should then observe the VMA as a whole
+	 * being marked soft-dirty.
+	 */
+	map2 = mremap(map2, pagesize, pagesize, MREMAP_FIXED | MREMAP_MAYMOVE,
+		      &reserved[2 * pagesize]);
+	if (map2 == MAP_FAILED)
+		ksft_exit_fail_msg("mremap failed\n");
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map) == 1,
+			 "Test %s-anon soft-dirty after merge 1st pg\n",
+			 __func__);
+	ksft_test_result(pagemap_is_softdirty(pagemap_fd, map2) == 1,
+			 "Test %s-anon soft-dirty after merge 2nd pg\n",
+			 __func__);
+
+	munmap(map, 2 * pagesize);
+}
+
 static void test_mprotect_anon(int pagemap_fd, int pagesize)
 {
 	test_mprotect(pagemap_fd, pagesize, true);
@@ -204,7 +252,7 @@ int main(int argc, char **argv)
 	if (!softdirty_supported())
 		ksft_exit_skip("soft-dirty is not support\n");
 
-	ksft_set_plan(15);
+	ksft_set_plan(17);
 	pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY);
 	if (pagemap_fd < 0)
 		ksft_exit_fail_msg("Failed to open %s\n", PAGEMAP_FILE_PATH);
@@ -216,6 +264,7 @@ int main(int argc, char **argv)
 	test_hugepage(pagemap_fd, pagesize);
 	test_mprotect_anon(pagemap_fd, pagesize);
 	test_mprotect_file(pagemap_fd, pagesize);
+	test_merge(pagemap_fd, pagesize);
 
 	close(pagemap_fd);
 
_

Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are

mm-shmem-update-shmem-to-use-mmap_prepare.patch
device-dax-update-devdax-to-use-mmap_prepare.patch
mm-vma-remove-unused-function-make-internal-functions-static.patch
mm-add-vma_desc_size-vma_desc_pages-helpers.patch
relay-update-relay-to-use-mmap_prepare.patch
mm-vma-rename-__mmap_prepare-function-to-avoid-confusion.patch
mm-add-remap_pfn_range_prepare-remap_pfn_range_complete.patch
mm-abstract-io_remap_pfn_range-based-on-pfn.patch
mm-introduce-io_remap_pfn_range_.patch
mm-add-ability-to-take-further-action-in-vm_area_desc.patch
doc-update-porting-vfs-documentation-for-mmap_prepare-actions.patch
mm-hugetlbfs-update-hugetlbfs-to-use-mmap_prepare.patch
mm-add-shmem_zero_setup_desc.patch
mm-update-mem-char-driver-to-use-mmap_prepare.patch
mm-update-resctl-to-use-mmap_prepare.patch
mm-vma-small-vma-lock-cleanups.patch
mm-introduce-vm_maybe_guard-and-make-visible-in-proc-pid-smaps.patch
mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such.patch
mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such-fix.patch
mm-implement-sticky-vma-flags.patch
mm-introduce-copy-on-fork-vmas-and-make-vm_maybe_guard-one.patch
mm-set-the-vm_maybe_guard-flag-on-guard-region-install.patch
mm-set-the-vm_maybe_guard-flag-on-guard-region-install-fix.patch
tools-testing-vma-add-vma-sticky-userland-tests.patch
tools-testing-selftests-mm-add-madv_collapse-test-case.patch
tools-testing-selftests-mm-add-smaps-visibility-guard-region-test.patch
mm-correctly-handle-uffd-pte-markers.patch
mm-introduce-leaf-entry-type-and-use-to-simplify-leaf-entry-logic.patch
mm-avoid-unnecessary-uses-of-is_swap_pte.patch
mm-eliminate-is_swap_pte-when-softleaf_from_pte-suffices.patch
mm-use-leaf-entries-in-debug-pgtable-remove-is_swap_pte.patch
fs-proc-task_mmu-refactor-pagemap_pmd_range.patch
mm-avoid-unnecessary-use-of-is_swap_pmd.patch
mm-huge_memory-refactor-copy_huge_pmd-non-present-logic.patch
mm-huge_memory-refactor-change_huge_pmd-non-present-logic.patch
mm-replace-pmd_to_swp_entry-with-softleaf_from_pmd.patch
mm-introduce-pmd_is_huge-and-use-where-appropriate.patch
mm-remove-remaining-is_swap_pmd-users-and-is_swap_pmd.patch
mm-remove-non_swap_entry-and-use-softleaf-helpers-instead.patch
mm-remove-is_hugetlb_entry_.patch
mm-eliminate-further-swapops-predicates.patch
mm-replace-remaining-pte_to_swp_entry-with-softleaf_from_pte.patch
mm-rename-walk_page_range_mm.patch
mm-madvise-allow-guard-page-install-remove-under-vma-lock.patch
mm-propagate-vm_softdirty-on-merge.patch
testing-selftests-mm-add-soft-dirty-merge-self-test.patch