Subject: [PATCH v2 2/4] mm: move vma_mmu_pagesize() from hugetlb to vma.c

From: "David Hildenbrand (Arm)" <[email-masked]>
Date: Mon, 9 Mar 2026 16:18:59 +0100

vma_mmu_pagesize() is also queried on non-hugetlb VMAs and does not
really belong into hugetlb.c.

PPC64 provides a custom overwrite with CONFIG_HUGETLB_PAGE, see
arch/powerpc/mm/book3s64/slice.c, so we cannot easily make this a
static inline function.

So let's move it to vma.c and add some proper kerneldoc.

To make vma tests happy, add a simple vma_kernel_pagesize() stub in
tools/testing/vma/include/custom.h.

Reviewed-by: Lorenzo Stoakes (Oracle) <[email-masked]>
Acked-by: Mike Rapoport (Microsoft) <[email-masked]>
Signed-off-by: David Hildenbrand (Arm) <[email-masked]>
---
 include/linux/hugetlb.h            |  7 -------
 include/linux/mm.h                 |  2 ++
 mm/hugetlb.c                       | 11 -----------
 mm/vma.c                           | 21 +++++++++++++++++++++
 tools/testing/vma/include/custom.h |  5 +++++
 5 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 44c1848a2c21..aaf3d472e6b5 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -777,8 +777,6 @@ static inline unsigned long huge_page_size(const struct hstate *h)
 	return (unsigned long)PAGE_SIZE << h->order;
 }
 
-extern unsigned long vma_mmu_pagesize(struct vm_area_struct *vma);
-
 static inline unsigned long huge_page_mask(struct hstate *h)
 {
 	return h->mask;
@@ -1175,11 +1173,6 @@ static inline unsigned long huge_page_mask(struct hstate *h)
 	return PAGE_MASK;
 }
 
-static inline unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
-{
-	return PAGE_SIZE;
-}
-
 static inline unsigned int huge_page_order(struct hstate *h)
 {
 	return 0;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 227809790f1a..22d338933c84 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1327,6 +1327,8 @@ static inline unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
 	return PAGE_SIZE;
 }
 
+unsigned long vma_mmu_pagesize(struct vm_area_struct *vma);
+
 static inline
 struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max)
 {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 66eadfa9e958..f6ecca9aae01 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1017,17 +1017,6 @@ static pgoff_t vma_hugecache_offset(struct hstate *h,
 			(vma->vm_pgoff >> huge_page_order(h));
 }
 
-/*
- * Return the page size being used by the MMU to back a VMA. In the majority
- * of cases, the page size used by the kernel matches the MMU size. On
- * architectures where it differs, an architecture-specific 'strong'
- * version of this symbol is required.
- */
-__weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
-{
-	return vma_kernel_pagesize(vma);
-}
-
 /*
  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
  * bits of the reservation map pointer, which are always clear due to
diff --git a/mm/vma.c b/mm/vma.c
index be64f781a3aa..e95fd5a5fe5c 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -3300,3 +3300,24 @@ int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 
 	return 0;
 }
+
+/**
+ * vma_mmu_pagesize - Default MMU page size granularity for this VMA.
+ * @vma: The user mapping.
+ *
+ * In the common case, the default page size used by the MMU matches the
+ * default page size used by the kernel (see vma_kernel_pagesize()). On
+ * architectures where it differs, an architecture-specific 'strong' version
+ * of this symbol is required.
+ *
+ * The default MMU page size is not affected by Transparent Huge Pages
+ * being in effect, or any usage of larger MMU page sizes (either through
+ * architectural huge-page mappings or other explicit/implicit coalescing of
+ * virtual ranges performed by the MMU).
+ *
+ * Return: The default MMU page size granularity for this VMA.
+ */
+__weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
+{
+	return vma_kernel_pagesize(vma);
+}
diff --git a/tools/testing/vma/include/custom.h b/tools/testing/vma/include/custom.h
index 802a76317245..4305a5b6e433 100644
--- a/tools/testing/vma/include/custom.h
+++ b/tools/testing/vma/include/custom.h
@@ -117,3 +117,8 @@ static inline vma_flags_t __mk_vma_flags(size_t count, const vma_flag_t *bits)
 			vma_flag_set(&flags, bits[i]);
 	return flags;
 }
+
+static inline unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
+{
+	return PAGE_SIZE;
+}
-- 
2.43.0