+ mm-introduce-vma_pgtable_walk_beginend.patch added to mm-unstable branch

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

The patch titled
     Subject: mm: introduce vma_pgtable_walk_{begin|end}()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-introduce-vma_pgtable_walk_beginend.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-introduce-vma_pgtable_walk_beginend.patch

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

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------------------------------------------------------
From: Peter Xu <peterx@redhat.com>
Subject: mm: introduce vma_pgtable_walk_{begin|end}()
Date: Wed, 27 Mar 2024 11:23:23 -0400

Introduce per-vma begin()/end() helpers for pgtable walks.  This is a
preparation work to merge hugetlb pgtable walkers with generic mm.

The helpers need to be called before and after a pgtable walk, will start
to be needed if the pgtable walker code supports hugetlb pages.  It's a
hook point for any type of VMA, but for now only hugetlb uses it to
stablize the pgtable pages from getting away (due to possible pmd
unsharing).

Link: https://lkml.kernel.org/r/20240327152332.950956-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |    3 +++
 mm/memory.c        |   12 ++++++++++++
 2 files changed, 15 insertions(+)

--- a/include/linux/mm.h~mm-introduce-vma_pgtable_walk_beginend
+++ a/include/linux/mm.h
@@ -4229,4 +4229,7 @@ static inline bool pfn_is_unaccepted_mem
 	return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE);
 }
 
+void vma_pgtable_walk_begin(struct vm_area_struct *vma);
+void vma_pgtable_walk_end(struct vm_area_struct *vma);
+
 #endif /* _LINUX_MM_H */
--- a/mm/memory.c~mm-introduce-vma_pgtable_walk_beginend
+++ a/mm/memory.c
@@ -6426,3 +6426,15 @@ void ptlock_free(struct ptdesc *ptdesc)
 	kmem_cache_free(page_ptl_cachep, ptdesc->ptl);
 }
 #endif
+
+void vma_pgtable_walk_begin(struct vm_area_struct *vma)
+{
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_lock_read(vma);
+}
+
+void vma_pgtable_walk_end(struct vm_area_struct *vma)
+{
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_unlock_read(vma);
+}
_

Patches currently in -mm which might be from peterx@redhat.com are

mm-hmm-process-pud-swap-entry-without-pud_huge.patch
mm-gup-cache-p4d-in-follow_p4d_mask.patch
mm-gup-check-p4d-presence-before-going-on.patch
mm-x86-change-pxd_huge-behavior-to-exclude-swap-entries.patch
mm-sparc-change-pxd_huge-behavior-to-exclude-swap-entries.patch
mm-arm-use-macros-to-define-pmd-pud-helpers.patch
mm-arm-redefine-pmd_huge-with-pmd_leaf.patch
mm-arm64-merge-pxd_huge-and-pxd_leaf-definitions.patch
mm-powerpc-redefine-pxd_huge-with-pxd_leaf.patch
mm-gup-merge-pxd-huge-mapping-checks.patch
mm-treewide-replace-pxd_huge-with-pxd_leaf.patch
mm-treewide-remove-pxd_huge.patch
mm-arm-remove-pmd_thp_or_huge.patch
mm-document-pxd_leaf-api.patch
selftests-mm-run_vmtestssh-fix-hugetlb-mem-size-calculation.patch
mm-kconfig-config_pgtable_has_huge_leaves.patch
mm-hugetlb-declare-hugetlbfs_pagecache_present-non-static.patch
mm-make-hpage_pxd_-macros-even-if-thp.patch
mm-introduce-vma_pgtable_walk_beginend.patch
mm-arch-provide-pud_pfn-fallback.patch
mm-gup-drop-folio_fast_pin_allowed-in-hugepd-processing.patch
mm-gup-refactor-record_subpages-to-find-1st-small-page.patch
mm-gup-handle-hugetlb-for-no_page_table.patch
mm-gup-cache-pudp-in-follow_pud_mask.patch
mm-gup-handle-huge-pud-for-follow_pud_mask.patch
mm-gup-handle-huge-pmd-for-follow_pmd_mask.patch
mm-gup-handle-hugepd-for-follow_page.patch
mm-gup-handle-hugetlb-in-the-generic-follow_page_mask-code.patch