[PATCH v2 2/4] mm: rename my_zero_pfn() to zero_pfn()

[Mike Rapoport <rppt@kernel.org>]

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