[PATCH v3 2/4] mm: rename my_zero_pfn() to zero_pfn()

Mike Rapoport
2026-02-11T10:32:26Z

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

my_zero_pfn() is a silly name.

Rename zero_pfn variable to zero_page_pfn and my_zero_pfn() function to
zero_pfn().

While on it, move extern declarations of zero_page_pfn outside the
functions that use it and add a comment about what ZERO_PAGE is.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
arch/x86/kvm/mmu/spte.h | 2 +-
fs/dax.c | 2 +-
fs/proc/vmcore.c | 2 +-
include/linux/pgtable.h | 28 ++++++++++++++++++++--------
mm/huge_memory.c | 2 +-
mm/memory.c | 2 +-
mm/migrate.c | 2 +-
mm/mm_init.c | 10 +++++-----
mm/userfaultfd.c | 4 ++--
9 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 91ce29fd6f1b..8c0ffa2cded6 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -248,7 +248,7 @@ extern u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;

static inline hpa_t kvm_mmu_get_dummy_root(void)
{
- return my_zero_pfn(0) << PAGE_SHIFT;
+ return zero_pfn(0) << PAGE_SHIFT;
}

static inline bool kvm_mmu_is_dummy_root(hpa_t shadow_page)
diff --git a/fs/dax.c b/fs/dax.c
index 289e6254aa30..b78cff9c91b3 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1360,7 +1360,7 @@ static vm_fault_t dax_load_hole(struct xa_state *xas, struct vm_fault *vmf,
{
struct inode *inode = iter->inode;
unsigned long vaddr = vmf->address;
- unsigned long pfn = my_zero_pfn(vaddr);
+ unsigned long pfn = zero_pfn(vaddr);
vm_fault_t ret;

*entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, DAX_ZERO_PAGE);
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index f188bd900eb2..44d15436439f 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -525,7 +525,7 @@ static int remap_oldmem_pfn_checked(struct vm_area_struct *vma,
{
unsigned long map_size;
unsigned long pos_start, pos_end, pos;
- unsigned long zeropage_pfn = my_zero_pfn(0);
+ unsigned long zeropage_pfn = zero_pfn(0);
size_t len = 0;

pos_start = pfn;
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 08a88b0d56e5..9bacf4df9769 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1882,27 +1882,39 @@ static inline void pfnmap_setup_cachemode_pfn(unsigned long pfn, pgprot_t *prot)
pfnmap_setup_cachemode(pfn, PAGE_SIZE, prot);
}

+/*
+ * ZERO_PAGE() is global shared page(s) that is always zero. It is used for
+ * zero-mapped memory areas, CoW etc.
+ *
+ * On architectures that __HAVE_COLOR_ZERO_PAGE there are several such pages
+ * for different ranges in the virtual address space.
+ *
+ * zero_page_pfn identifies the first (or the only) pfn for these pages.
+ */
#ifdef __HAVE_COLOR_ZERO_PAGE
static inline int is_zero_pfn(unsigned long pfn)
{
- extern unsigned long zero_pfn;
- unsigned long offset_from_zero_pfn = pfn - zero_pfn;
+ extern unsigned long zero_page_pfn;
+ unsigned long offset_from_zero_pfn = pfn - zero_page_pfn;
+
return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
}

-#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))
+#define zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))

#else
static inline int is_zero_pfn(unsigned long pfn)
{
- extern unsigned long zero_pfn;
- return pfn == zero_pfn;
+ extern unsigned long zero_page_pfn;
+
+ return pfn == zero_page_pfn;
}

-static inline unsigned long my_zero_pfn(unsigned long addr)
+static inline unsigned long zero_pfn(unsigned long addr)
{
- extern unsigned long zero_pfn;
- return zero_pfn;
+ extern unsigned long zero_page_pfn;
+
+ return zero_page_pfn;
}
#endif /* __HAVE_COLOR_ZERO_PAGE */

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 44ff8a648afd..bc15fd152526 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2968,7 +2968,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
pte_t entry;

- entry = pfn_pte(my_zero_pfn(addr), vma->vm_page_prot);
+ entry = pfn_pte(zero_pfn(addr), vma->vm_page_prot);
entry = pte_mkspecial(entry);
if (pmd_uffd_wp(old_pmd))
entry = pte_mkuffd_wp(entry);
diff --git a/mm/memory.c b/mm/memory.c
index 51d2018a387a..ae610afa9cea 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5165,7 +5165,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
/* Use the zero-page for reads */
if (!(vmf->flags & FAULT_FLAG_WRITE) &&
!mm_forbids_zeropage(vma->vm_mm)) {
- entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
+ entry = pte_mkspecial(pfn_pte(zero_pfn(vmf->address),
vma->vm_page_prot));
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
diff --git a/mm/migrate.c b/mm/migrate.c
index 1bf2cf8c44dd..739c4e03769b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -321,7 +321,7 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw,
if (!pages_identical(page, ZERO_PAGE(0)))
return false;

- newpte = pte_mkspecial(pfn_pte(my_zero_pfn(pvmw->address),
+ newpte = pte_mkspecial(pfn_pte(zero_pfn(pvmw->address),
pvmw->vma->vm_page_prot));

if (pte_swp_soft_dirty(old_pte))
diff --git a/mm/mm_init.c b/mm/mm_init.c
index dcf9eff34f83..a0ca236eb4f5 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -53,8 +53,8 @@ EXPORT_SYMBOL(mem_map);
void *high_memory;
EXPORT_SYMBOL(high_memory);

-unsigned long zero_pfn __ro_after_init;
-EXPORT_SYMBOL(zero_pfn);
+unsigned long zero_page_pfn __ro_after_init;
+EXPORT_SYMBOL(zero_page_pfn);

#ifdef CONFIG_DEBUG_MEMORY_INIT
int __meminitdata mminit_loglevel;
@@ -2670,12 +2670,12 @@ static void __init mem_init_print_info(void)
);
}

-static int __init init_zero_pfn(void)
+static int __init init_zero_page_pfn(void)
{
- zero_pfn = page_to_pfn(ZERO_PAGE(0));
+ zero_page_pfn = page_to_pfn(ZERO_PAGE(0));
return 0;
}
-early_initcall(init_zero_pfn);
+early_initcall(init_zero_page_pfn);

void __init __weak arch_mm_preinit(void)
{
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 927086bb4a3c..e19872e51878 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -357,7 +357,7 @@ static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd,
if (mm_forbids_zeropage(dst_vma->vm_mm))
return mfill_atomic_pte_zeroed_folio(dst_pmd, dst_vma, dst_addr);

- _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
+ _dst_pte = pte_mkspecial(pfn_pte(zero_pfn(dst_addr),
dst_vma->vm_page_prot));
ret = -EAGAIN;
dst_pte = pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl);
@@ -1229,7 +1229,7 @@ static int move_zeropage_pte(struct mm_struct *mm,
return -EAGAIN;
}

- zero_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
+ zero_pte = pte_mkspecial(pfn_pte(zero_pfn(dst_addr),
dst_vma->vm_page_prot));
ptep_clear_flush(src_vma, src_addr, src_pte);
set_pte_at(mm, dst_addr, dst_pte, zero_pte);
--
2.51.0