+ mm-memory-factor-out-common-code-from-vm_normal_page_.patch added to mm-new branch

+ mm-memory-factor-out-common-code-from-vm_normal_page_.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/memory: factor out common code from vm_normal_page_*()
has been added to the -mm mm-new branch.  Its filename is
     mm-memory-factor-out-common-code-from-vm_normal_page_.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-factor-out-common-code-from-vm_normal_page_.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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   a) Consider who else should be cc'ed
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/memory: factor out common code from vm_normal_page_*()
Date: Mon, 11 Aug 2025 13:26:29 +0200

Let's reduce the code duplication and factor out the non-pte/pmd related
magic into __vm_normal_page().

To keep it simpler, check the pfn against both zero folios, which
shouldn't really make a difference.

It's a good question if we can even hit the !CONFIG_ARCH_HAS_PTE_SPECIAL
scenario in the PMD case in practice: but doesn't really matter, as it's
now all unified in vm_normal_page_pfn().

Add kerneldoc for all involved functions.

Note that, as a side product, we now:
* Support the find_special_page special thingy also for PMD
* Don't check for is_huge_zero_pfn() anymore if we have
  CONFIG_ARCH_HAS_PTE_SPECIAL and the PMD is not special. The
  VM_WARN_ON_ONCE would catch any abuse

No functional change intended.

Link: https://lkml.kernel.org/r/20250811112631.759341-10-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Juegren Gross <jgross@suse.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory.c |  186 +++++++++++++++++++++++++++++---------------------
 1 file changed, 109 insertions(+), 77 deletions(-)

--- a/mm/memory.c~mm-memory-factor-out-common-code-from-vm_normal_page_
+++ a/mm/memory.c
@@ -614,8 +614,14 @@ static void print_bad_page_map(struct vm
 #define print_bad_pte(vma, addr, pte, page) \
 	print_bad_page_map(vma, addr, pte_val(pte), page, PGTABLE_LEVEL_PTE)
 
-/*
- * vm_normal_page -- This function gets the "struct page" associated with a pte.
+/**
+ * __vm_normal_page() - Get the "struct page" associated with a page table entry.
+ * @vma: The VMA mapping the page table entry.
+ * @addr: The address where the page table entry is mapped.
+ * @pfn: The PFN stored in the page table entry.
+ * @special: Whether the page table entry is marked "special".
+ * @level: The page table level for error reporting purposes only.
+ * @entry: The page table entry value for error reporting purposes only.
  *
  * "Special" mappings do not wish to be associated with a "struct page" (either
  * it doesn't exist, or it exists but they don't want to touch it). In this
@@ -628,10 +634,10 @@ static void print_bad_page_map(struct vm
  * Selected page table walkers (such as GUP) can still identify mappings of the
  * shared zero folios and work with the underlying "struct page".
  *
- * There are 2 broad cases. Firstly, an architecture may define a pte_special()
- * pte bit, in which case this function is trivial. Secondly, an architecture
- * may not have a spare pte bit, which requires a more complicated scheme,
- * described below.
+ * There are 2 broad cases. Firstly, an architecture may define a "special"
+ * page table entry bit, such as pte_special(), in which case this function is
+ * trivial. Secondly, an architecture may not have a spare page table
+ * entry bit, which requires a more complicated scheme, described below.
  *
  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
  * special mapping (even if there are underlying and valid "struct pages").
@@ -664,63 +670,94 @@ static void print_bad_page_map(struct vm
  * don't have to follow the strict linearity rule of PFNMAP mappings in
  * order to support COWable mappings.
  *
+ * Return: Returns the "struct page" if this is a "normal" mapping. Returns
+ *	   NULL if this is a "special" mapping.
  */
-struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
-			    pte_t pte)
+static inline struct page *__vm_normal_page(struct vm_area_struct *vma,
+		unsigned long addr, unsigned long pfn, bool special,
+		unsigned long long entry, enum pgtable_level level)
 {
-	unsigned long pfn = pte_pfn(pte);
-
 	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
-		if (likely(!pte_special(pte)))
-			goto check_pfn;
-		if (vma->vm_ops && vma->vm_ops->find_special_page)
-			return vma->vm_ops->find_special_page(vma, addr);
-		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
-			return NULL;
-		if (is_zero_pfn(pfn))
-			return NULL;
-
-		print_bad_pte(vma, addr, pte, NULL);
-		return NULL;
-	}
-
-	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
-
-	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
-		if (vma->vm_flags & VM_MIXEDMAP) {
-			if (!pfn_valid(pfn))
-				return NULL;
-			if (is_zero_pfn(pfn))
+		if (unlikely(special)) {
+			if (vma->vm_ops && vma->vm_ops->find_special_page)
+				return vma->vm_ops->find_special_page(vma, addr);
+			if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
 				return NULL;
-			goto out;
-		} else {
-			unsigned long off;
-			off = (addr - vma->vm_start) >> PAGE_SHIFT;
-			if (pfn == vma->vm_pgoff + off)
-				return NULL;
-			if (!is_cow_mapping(vma->vm_flags))
+			if (is_zero_pfn(pfn) || is_huge_zero_pfn(pfn))
 				return NULL;
+
+			print_bad_page_map(vma, addr, entry, NULL, level);
+			return NULL;
+		}
+		/*
+		 * With CONFIG_ARCH_HAS_PTE_SPECIAL, any special page table
+		 * mappings (incl. shared zero folios) are marked accordingly.
+		 */
+	} else {
+		if (unlikely(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))) {
+			if (vma->vm_flags & VM_MIXEDMAP) {
+				/* If it has a "struct page", it's "normal". */
+				if (!pfn_valid(pfn))
+					return NULL;
+			} else {
+				unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT;
+
+				/* Only CoW'ed anon folios are "normal". */
+				if (pfn == vma->vm_pgoff + off)
+					return NULL;
+				if (!is_cow_mapping(vma->vm_flags))
+					return NULL;
+			}
 		}
-	}
 
-	if (is_zero_pfn(pfn))
-		return NULL;
+		if (is_zero_pfn(pfn) || is_huge_zero_pfn(pfn))
+			return NULL;
+	}
 
-check_pfn:
 	if (unlikely(pfn > highest_memmap_pfn)) {
-		print_bad_pte(vma, addr, pte, NULL);
+		/* Corrupted page table entry. */
+		print_bad_page_map(vma, addr, entry, NULL, level);
 		return NULL;
 	}
-
 	/*
 	 * NOTE! We still have PageReserved() pages in the page tables.
-	 * eg. VDSO mappings can cause them to exist.
+	 * For example, VDSO mappings can cause them to exist.
 	 */
-out:
-	VM_WARN_ON_ONCE(is_zero_pfn(pfn));
+	VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn));
 	return pfn_to_page(pfn);
 }
 
+/**
+ * vm_normal_page() - Get the "struct page" associated with a PTE
+ * @vma: The VMA mapping the @pte.
+ * @addr: The address where the @pte is mapped.
+ * @pte: The PTE.
+ *
+ * Get the "struct page" associated with a PTE. See __vm_normal_page()
+ * for details on "normal" and "special" mappings.
+ *
+ * Return: Returns the "struct page" if this is a "normal" mapping. Returns
+ *	   NULL if this is a "special" mapping.
+ */
+struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+			    pte_t pte)
+{
+	return __vm_normal_page(vma, addr, pte_pfn(pte), pte_special(pte),
+				pte_val(pte), PGTABLE_LEVEL_PTE);
+}
+
+/**
+ * vm_normal_folio() - Get the "struct folio" associated with a PTE
+ * @vma: The VMA mapping the @pte.
+ * @addr: The address where the @pte is mapped.
+ * @pte: The PTE.
+ *
+ * Get the "struct folio" associated with a PTE. See __vm_normal_page()
+ * for details on "normal" and "special" mappings.
+ *
+ * Return: Returns the "struct folio" if this is a "normal" mapping. Returns
+ *	   NULL if this is a "special" mapping.
+ */
 struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr,
 			    pte_t pte)
 {
@@ -732,42 +769,37 @@ struct folio *vm_normal_folio(struct vm_
 }
 
 #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
+/**
+ * vm_normal_page_pmd() - Get the "struct page" associated with a PMD
+ * @vma: The VMA mapping the @pmd.
+ * @addr: The address where the @pmd is mapped.
+ * @pmd: The PMD.
+ *
+ * Get the "struct page" associated with a PTE. See __vm_normal_page()
+ * for details on "normal" and "special" mappings.
+ *
+ * Return: Returns the "struct page" if this is a "normal" mapping. Returns
+ *	   NULL if this is a "special" mapping.
+ */
 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
 				pmd_t pmd)
 {
-	unsigned long pfn = pmd_pfn(pmd);
-
-	if (unlikely(pmd_special(pmd)))
-		return NULL;
-
-	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
-		if (vma->vm_flags & VM_MIXEDMAP) {
-			if (!pfn_valid(pfn))
-				return NULL;
-			goto out;
-		} else {
-			unsigned long off;
-			off = (addr - vma->vm_start) >> PAGE_SHIFT;
-			if (pfn == vma->vm_pgoff + off)
-				return NULL;
-			if (!is_cow_mapping(vma->vm_flags))
-				return NULL;
-		}
-	}
-
-	if (is_huge_zero_pfn(pfn))
-		return NULL;
-	if (unlikely(pfn > highest_memmap_pfn))
-		return NULL;
-
-	/*
-	 * NOTE! We still have PageReserved() pages in the page tables.
-	 * eg. VDSO mappings can cause them to exist.
-	 */
-out:
-	return pfn_to_page(pfn);
+	return __vm_normal_page(vma, addr, pmd_pfn(pmd), pmd_special(pmd),
+				pmd_val(pmd), PGTABLE_LEVEL_PMD);
 }
 
+/**
+ * vm_normal_folio_pmd() - Get the "struct folio" associated with a PMD
+ * @vma: The VMA mapping the @pmd.
+ * @addr: The address where the @pmd is mapped.
+ * @pmd: The PMD.
+ *
+ * Get the "struct folio" associated with a PTE. See __vm_normal_page()
+ * for details on "normal" and "special" mappings.
+ *
+ * Return: Returns the "struct folio" if this is a "normal" mapping. Returns
+ *	   NULL if this is a "special" mapping.
+ */
 struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
 				  unsigned long addr, pmd_t pmd)
 {
_

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

mm-migrate-remove-migratepage_unmap.patch
treewide-remove-migratepage_success.patch
mm-huge_memory-move-more-common-code-into-insert_pmd.patch
mm-huge_memory-move-more-common-code-into-insert_pud.patch
mm-huge_memory-support-huge-zero-folio-in-vmf_insert_folio_pmd.patch
fs-dax-use-vmf_insert_folio_pmd-to-insert-the-huge-zero-folio.patch
mm-huge_memory-mark-pmd-mappings-of-the-huge-zero-folio-special.patch
mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level.patch
mm-memory-convert-print_bad_pte-to-print_bad_page_map.patch
mm-memory-factor-out-common-code-from-vm_normal_page_.patch
mm-introduce-and-use-vm_normal_page_pud.patch
mm-rename-vm_ops-find_special_page-to-vm_ops-find_normal_page.patch