diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2fc7fdd..ab79cd4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -262,7 +262,7 @@
 	struct list_head regions;
 };
 
-struct resv_map *resv_map_alloc(void)
+static struct resv_map *resv_map_alloc(void)
 {
 	struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
 	if (!resv_map)
@@ -274,7 +274,7 @@
 	return resv_map;
 }
 
-void resv_map_release(struct kref *ref)
+static void resv_map_release(struct kref *ref)
 {
 	struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
 
@@ -289,7 +289,7 @@
 	if (!(vma->vm_flags & VM_SHARED))
 		return (struct resv_map *)(get_vma_private_data(vma) &
 							~HPAGE_RESV_MASK);
-	return 0;
+	return NULL;
 }
 
 static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
@@ -1747,10 +1747,8 @@
  * from other VMAs and let the children be SIGKILLed if they are faulting the
  * same region.
  */
-int unmap_ref_private(struct mm_struct *mm,
-					struct vm_area_struct *vma,
-					struct page *page,
-					unsigned long address)
+static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
+				struct page *page, unsigned long address)
 {
 	struct vm_area_struct *iter_vma;
 	struct address_space *mapping;