mm: move huge_zero_page declaration from huge_mm.h to mm.h

Move the declaration associated with huge_zero_page from huge_mm.h to
mm.h. This patch is in preparation for adding static PMD zero page as we
will be reusing some of the huge_zero_page infrastructure.

No functional changes.

Signed-off-by: Pankaj Raghav <[email protected]>

Author: Panky-codes

include/linux/huge_mm.h

@@ -478,22 +478,6 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 
 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf);
 
-extern struct folio *huge_zero_folio;
-extern unsigned long huge_zero_pfn;
-
-static inline bool is_huge_zero_folio(const struct folio *folio)
-{
-	return READ_ONCE(huge_zero_folio) == folio;
-}
-
-static inline bool is_huge_zero_pmd(pmd_t pmd)
-{
-	return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd);
-}
-
-struct folio *mm_get_huge_zero_folio(struct mm_struct *mm);
-void mm_put_huge_zero_folio(struct mm_struct *mm);
-
 static inline bool thp_migration_supported(void)
 {
 	return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION);
@@ -631,21 +615,6 @@ static inline vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	return 0;
 }
 
-static inline bool is_huge_zero_folio(const struct folio *folio)
-{
-	return false;
-}
-
-static inline bool is_huge_zero_pmd(pmd_t pmd)
-{
-	return false;
-}
-
-static inline void mm_put_huge_zero_folio(struct mm_struct *mm)
-{
-	return;
-}
-
 static inline struct page *follow_devmap_pmd(struct vm_area_struct *vma,
 	unsigned long addr, pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 {

include/linux/mm.h

@@ -4018,6 +4018,40 @@ static inline bool vma_is_special_huge(const struct vm_area_struct *vma)
 
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+extern struct folio *huge_zero_folio;
+extern unsigned long huge_zero_pfn;
+
+static inline bool is_huge_zero_folio(const struct folio *folio)
+{
+	return READ_ONCE(huge_zero_folio) == folio;
+}
+
+static inline bool is_huge_zero_pmd(pmd_t pmd)
+{
+	return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd);
+}
+
+struct folio *mm_get_huge_zero_folio(struct mm_struct *mm);
+void mm_put_huge_zero_folio(struct mm_struct *mm);
+
+#else
+static inline bool is_huge_zero_folio(const struct folio *folio)
+{
+	return false;
+}
+
+static inline bool is_huge_zero_pmd(pmd_t pmd)
+{
+	return false;
+}
+
+static inline void mm_put_huge_zero_folio(struct mm_struct *mm)
+{
+	return;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
 #if MAX_NUMNODES > 1
 void __init setup_nr_node_ids(void);
 #else