[PATCH v2 8/9] mm: introduce and use vm_normal_page_pud()

David Hildenbrand
2025-07-17T11:52:38Z

Let's introduce vm_normal_page_pud(), which ends up being fairly simple
because of our new common helpers and there not being a PUD-sized zero
folio.

Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO,
structuring the code like the other (pmd/pte) cases. Defer
introducing vm_normal_folio_pud() until really used.

Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mm.h | 2 ++
mm/memory.c | 27 +++++++++++++++++++++++++++
mm/pagewalk.c | 20 ++++++++++----------
3 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index abc47f1f307fb..0eb991262fbbf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2349,6 +2349,8 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd);
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t pmd);
+struct page *vm_normal_page_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t pud);

void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
diff --git a/mm/memory.c b/mm/memory.c
index c43ae5e4d7644..00a0d7ae3ba4a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -796,6 +796,33 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
return page_folio(page);
return NULL;
}
+
+/**
+ * vm_normal_page_pud() - Get the "struct page" associated with a PUD
+ * @vma: The VMA mapping the @pud.
+ * @addr: The address where the @pud is mapped.
+ * @pud: The PUD.
+ *
+ * Get the "struct page" associated with a PUD. See vm_normal_page_pfn()
+ * for details.
+ *
+ * Return: Returns the "struct page" if this is a "normal" mapping. Returns
+ * NULL if this is a "special" mapping.
+ */
+struct page *vm_normal_page_pud(struct vm_area_struct *vma,
+ unsigned long addr, pud_t pud)
+{
+ unsigned long pfn = pud_pfn(pud);
+
+ if (unlikely(pud_special(pud))) {
+ if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
+ return NULL;
+
+ print_bad_page_map(vma, addr, pud_val(pud), NULL);
+ return NULL;
+ }
+ return vm_normal_page_pfn(vma, addr, pfn, pud_val(pud));
+}
#endif

/**
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 648038247a8d2..c6753d370ff4e 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -902,23 +902,23 @@ struct folio *folio_walk_start(struct folio_walk *fw,
fw->pudp = pudp;
fw->pud = pud;

- /*
- * TODO: FW_MIGRATION support for PUD migration entries
- * once there are relevant users.
- */
- if (!pud_present(pud) || pud_special(pud)) {
+ if (pud_none(pud)) {
spin_unlock(ptl);
goto not_found;
- } else if (!pud_leaf(pud)) {
+ } else if (pud_present(pud) && !pud_leaf(pud)) {
spin_unlock(ptl);
goto pmd_table;
+ } else if (pud_present(pud)) {
+ page = vm_normal_page_pud(vma, addr, pud);
+ if (page)
+ goto found;
}
/*
- * TODO: vm_normal_page_pud() will be handy once we want to
- * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs.
+ * TODO: FW_MIGRATION support for PUD migration entries
+ * once there are relevant users.
*/
- page = pud_page(pud);
- goto found;
+ spin_unlock(ptl);
+ goto not_found;
}

pmd_table:
--
2.50.1