mm: export various functions for the benefit of DAX

To use the huge zero page in DAX, we need these functions exported.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/huge_mm.h

@@ -155,6 +155,16 @@ static inline bool is_huge_zero_page(struct page *page)
 	return ACCESS_ONCE(huge_zero_page) == page;
 }
 
+static inline bool is_huge_zero_pmd(pmd_t pmd)
+{
+	return is_huge_zero_page(pmd_page(pmd));
+}
+
+struct page *get_huge_zero_page(void);
+bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+		struct vm_area_struct *vma, unsigned long haddr,
+		pmd_t *pmd, struct page *zero_page);
+
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
 #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })

mm/huge_memory.c

@@ -173,12 +173,7 @@ fail:
 static atomic_t huge_zero_refcount;
 struct page *huge_zero_page __read_mostly;
 
-static inline bool is_huge_zero_pmd(pmd_t pmd)
-{
-	return is_huge_zero_page(pmd_page(pmd));
-}
-
-static struct page *get_huge_zero_page(void)
+struct page *get_huge_zero_page(void)
 {
 	struct page *zero_page;
 retry: