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 | 25 +++++++++++++++++--------
 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, 30 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..a965e2f8b8de 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1882,27 +1882,36 @@ 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.
+ */
+extern unsigned long zero_page_pfn;
+
 #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;
+	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;
+	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;
+	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

On Mon, Feb 09, 2026 at 04:40:55PM +0200, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> my_zero_pfn() is a silly name.

Is it too late to ask for it to be renamed to lorenzos_zero_pfn()? I've long
felt it was mine, due to the previous naming, and I feel like maybe it's time to
make it official... ;)

On Tue, Feb 10, 2026 at 02:52:56PM +0000, Lorenzo Stoakes wrote:
> On Mon, Feb 09, 2026 at 04:40:55PM +0200, Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> >
> > my_zero_pfn() is a silly name.
> 
> Is it too late to ask for it to be renamed to lorenzos_zero_pfn()? I've long
> felt it was mine, due to the previous naming, and I feel like maybe it's time to
> make it official... ;)

It's not too late, but the pfn will go to the highest bidder ;-P

-- 
Sincerely yours,
Mike.

Le 09/02/2026 à 15:40, Mike Rapoport a écrit :
> 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.

I guess the idea of the extern declaration being inside its only 
external users was to ensure nobody would start using it directly, hence 
bypassing the overloadable helpers.

Should we at least call the variable __zero_page_pfn instead in order to 
warn people that using it directly requires care ?

Christophe

On Mon, Feb 09, 2026 at 04:08:32PM +0100, Christophe Leroy (CS GROUP) wrote:
> 
> 
> Le 09/02/2026 à 15:40, Mike Rapoport a écrit :
> > 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.
> 
> I guess the idea of the extern declaration being inside its only external
> users was to ensure nobody would start using it directly, hence bypassing
> the overloadable helpers.
> 
> Should we at least call the variable __zero_page_pfn instead in order to
> warn people that using it directly requires care ?

I'd better move it back inside the helpers.
 
> Christophe
> 

-- 
Sincerely yours,
Mike.