+ mm-introduce-and-use-linear_folio_page_index.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: introduce and use linear_folio_page_index()
has been added to the -mm mm-new branch.  Its filename is
     mm-introduce-and-use-linear_folio_page_index.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-introduce-and-use-linear_folio_page_index.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: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm: introduce and use linear_folio_page_index()
Date: Mon, 20 Jul 2026 15:38:34 +0100

This function is, for now, a placeholder; it will be used in future to
determine whether to use the virtual page index or not, based on whether
the folio is anonymous or not.

Currently it simply wraps linear_page_index(), so this does not change
behaviour.

We update callers that will, once the change is introduced to track
anonymous folios by virtual page offset if MAP_PRIVATE file-backed, need
to determine which index to use based on folio type.

No functional change intended.

Link: https://lore.kernel.org/20260720-b4-scalable-cow-virt-pgoff-v2-8-2d549757a76f@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: Harry Yoo <harry@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/pagemap.h |   18 ++++++++++++++++++
 mm/huge_memory.c        |    3 ++-
 mm/migrate.c            |    6 ++++--
 mm/userfaultfd.c        |    6 ++++--
 4 files changed, 28 insertions(+), 5 deletions(-)

--- a/include/linux/pagemap.h~mm-introduce-and-use-linear_folio_page_index
+++ a/include/linux/pagemap.h
@@ -1143,6 +1143,24 @@ static inline pgoff_t linear_virt_page_i
 	return pgoff;
 }
 
+/**
+ * linear_folio_page_index() - Determine the absolute page offset of
+ * @address within @vma from @folio.
+ * @folio: The folio whose linear page index is sought.
+ * @vma: The VMA in which @address resides.
+ * @address: The address whose absolute page offset is required.
+ *
+ * For compatibility, currently identical to linear_page_index().
+ *
+ * Returns: The absolute page offset of @address within @vma.
+ */
+static inline pgoff_t linear_folio_page_index(const struct folio *folio,
+					      const struct vm_area_struct *vma,
+					      const unsigned long address)
+{
+	return linear_page_index(vma, address);
+}
+
 struct wait_page_key {
 	struct folio *folio;
 	int bit_nr;
--- a/mm/huge_memory.c~mm-introduce-and-use-linear_folio_page_index
+++ a/mm/huge_memory.c
@@ -2887,7 +2887,8 @@ int move_pages_huge_pmd(struct mm_struct
 		}
 
 		folio_move_anon_rmap(src_folio, dst_vma);
-		src_folio->index = linear_page_index(dst_vma, dst_addr);
+		src_folio->index = linear_folio_page_index(src_folio, dst_vma,
+							   dst_addr);
 
 		_dst_pmd = folio_mk_pmd(src_folio, dst_vma->vm_page_prot);
 		/* Follow mremap() behavior and treat the entry dirty after the move */
--- a/mm/migrate.c~mm-introduce-and-use-linear_folio_page_index
+++ a/mm/migrate.c
@@ -363,8 +363,10 @@ static bool remove_migration_pte(struct
 		unsigned long idx = 0;
 
 		/* pgoff is invalid for ksm pages, but they are never large */
-		if (folio_test_large(folio) && !folio_test_hugetlb(folio))
-			idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff;
+		if (folio_test_large(folio) && !folio_test_hugetlb(folio)) {
+			idx += linear_folio_page_index(folio, vma, pvmw.address);
+			idx -= pvmw.pgoff;
+		}
 		new = folio_page(folio, idx);
 
 #ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
--- a/mm/userfaultfd.c~mm-introduce-and-use-linear_folio_page_index
+++ a/mm/userfaultfd.c
@@ -1352,7 +1352,8 @@ static long move_present_ptes(struct mm_
 		}
 
 		folio_move_anon_rmap(src_folio, dst_vma);
-		src_folio->index = linear_page_index(dst_vma, dst_addr);
+		src_folio->index = linear_folio_page_index(src_folio, dst_vma,
+							   dst_addr);
 
 		orig_dst_pte = folio_mk_pte(src_folio, dst_vma->vm_page_prot);
 		/* Set soft dirty bit so userspace can notice the pte was moved */
@@ -1428,7 +1429,8 @@ static int move_swap_pte(struct mm_struc
 	 */
 	if (src_folio) {
 		folio_move_anon_rmap(src_folio, dst_vma);
-		src_folio->index = linear_page_index(dst_vma, dst_addr);
+		src_folio->index = linear_folio_page_index(src_folio, dst_vma,
+							   dst_addr);
 	} else {
 		/*
 		 * Check if the swap entry is cached after acquiring the src_pte
_

Patches currently in -mm which might be from ljs@kernel.org are

mm-vmalloc-acquire-init_mm-lock-on-huge-vmap-to-avoid-ptdump-uaf.patch
x86-mm-pat-acquire-init_mm-write-lock-on-collapse-to-avoid-uaf.patch
x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch
mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch
arm64-remove-redundant-concurrent-ptdump-uaf-mitigation.patch
mm-move-alloc-tag-to-mm.patch
mm-move-vma_start_pgoff-into-mmh-and-clean-up.patch
mm-add-kdoc-comments-for-vma_start-last_pgoff.patch
tools-testing-vma-use-vma_start_pgoff-in-merge-tests.patch
mm-introduce-and-use-vma_end_pgoff.patch
mm-rmap-update-mm-interval_treec-comments.patch
mm-rmap-parameterise-vma_interval_tree_-by-address_space.patch
mm-rmap-elide-unnecessary-static-inlines-in-interval_treec.patch
mm-rmap-rename-vma_interval_tree_-to-mapping_rmap_tree_.patch
mm-rmap-parameterise-anon_vma_interval_tree_-by-anon_vma.patch
mm-rmap-rename-anon_vma_interval_tree_-params-and-use-pgoff_t.patch
mm-rmap-rename-anon_vma_interval_tree_-to-anon_rmap_tree_.patch
maintainers-move-mm-interval_treec-to-rmap-section.patch
mm-vma-introduce-and-use-vmg_pages-vmg__pgoff.patch
mm-vma-clean-up-anon_vma_compatible.patch
mm-vma-refactor-vmg_adjust_set_range-for-clarity.patch
mm-vma-minor-cleanup-of-expand_.patch
mm-introduce-and-use-linear_page_delta.patch
mm-vma-use-vma_start_pgoff-linear_page_index-in-mm-code.patch
mm-prefer-vma__pgoff-to-vma-vm_pgoff-in-kernel.patch
mm-vma-remove-duplicative-vma_pgoff_offset-helper.patch
mm-use-linear_page_-consistently.patch
mm-vma-introduce-vma_assert_can_modify.patch
mm-vma-add-and-use-vma__pgoff.patch
mm-vma-move-__install_special_mapping-to-vmac.patch
mm-vma-make-vma_set_range-static-drop-insert_vm_struct-decl.patch
mm-vma-update-vma_shrink-to-not-pass-start-pgoff-parameters.patch
mm-vma-update-vmg_adjust_set_range-to-offset-pgoff-instead.patch
mm-vma-slightly-rework-the-anonymous-check-in-__mmap_new_vma.patch
mm-vma-introduce-and-use-vma_set_pgoff.patch
mm-vma-correct-incorrect-vmah-inclusion.patch
mm-vma-use-guard-clauses-in-can_vma_merge_.patch
tools-testing-vma-default-vma-mm-flag-bits-to-64-bit.patch
tools-testing-vma-output-compared-expression-on-assert_.patch
mm-introduce-vma_flags_can_grow-and-vma_can_grow.patch
mm-vma-update-do_mmap-to-use-vma_flags_t.patch
mm-convert-__get_unmapped_area-to-use-vma_flags_t.patch
mm-update-generic_get_unmapped_area-to-use-vma_flags_t.patch
mm-prefer-mm-def_vma_flags-in-mm-logic.patch
mm-vma-convert-vm_pgprot_modify-to-use-vma_flags_t-and-rename.patch
mm-vma-rename-vma_get_page_prot-to-vma_flags_to_page_prot.patch
mm-introduce-vma_get_page_prot-and-use-it.patch
mm-vma-update-create_init_stack_vma-to-use-vma_flags_t.patch
mm-vma-convert-miscellaneous-uses-of-vma-flags-in-core-mm.patch
mm-mlock-convert-mlock-code-to-use-vma_flags_t.patch
mm-mprotect-convert-mprotect-code-to-use-vma_flags_t.patch
mm-mremap-convert-mremap-code-to-use-vma_flags_t.patch
mm-mseal-remove-superfluous-comments-fix-confusion-around-mm.patch
mm-mseal-limit-scope-of-mseal-address-zero-to-address-zero.patch
mm-mseal-remove-further-superfluous-comments-do_mseal.patch
mm-vma-introduce-vma-virtual-page-offset-field-and-add-helpers.patch
mm-introduce-linear_virt_page_index.patch
mm-abstract-vma_address-and-introduce-vma_anon_address.patch
mm-update-print_bad_page_map-to-show-virtual-page-index.patch
mm-introduce-and-use-vma_filebacked_address.patch
mm-propagate-vma-virtual-page-offset-on-map-remap-split-merge.patch
mm-rmap-track-whether-the-page-vma-mapped-walk-is-anonymous.patch
mm-introduce-and-use-linear_folio_page_index.patch
mm-rmap-use-virt-pgoff-for-map_private-file-backed-anon-folios.patch
tools-testing-vma-expand-vma-merge-tests-to-assert-virt-pgoff.patch
tools-testing-selftests-mm-test-virtual-page-offset-merge-behaviour.patch
mm-vma-only-permit-map_private-dev-zero-to-be-mapped-anonymous.patch
mm-vma-make-map_private-mapped-dev-zero-mappings-truly-anonymous.patch
tools-testing-vma-add-test-to-assert-map_private-dev-zero-is-anon.patch
tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch