2 files changed, 31 insertions, 7 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 251233c1494d..d01cc972a1d9 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -31,7 +31,6 @@ struct hugepage_subpool *hugepage_new_subpool(long nr_blocks);
 void hugepage_put_subpool(struct hugepage_subpool *spool);
 
 int PageHuge(struct page *page);
-int PageHeadHuge(struct page *page_head);
 
 void reset_vma_resv_huge_pages(struct vm_area_struct *vma);
 int hugetlb_sysctl_handler(struct ctl_table *, int, void __user *, size_t *, loff_t *);
@@ -104,11 +103,6 @@ static inline int PageHuge(struct page *page)
         return 0;
 }
 
-static inline int PageHeadHuge(struct page *page_head)
-{
-        return 0;
-}
-
 static inline void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
 {
 }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9fac6dd69b11..f95c71b7c1fd 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -414,15 +414,45 @@ static inline int page_count(struct page *page)
         return atomic_read(&compound_head(page)->_count);
 }
 
+#ifdef CONFIG_HUGETLB_PAGE
+extern int PageHeadHuge(struct page *page_head);
+#else /* CONFIG_HUGETLB_PAGE */
+static inline int PageHeadHuge(struct page *page_head)
+{
+        return 0;
+}
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static inline bool __compound_tail_refcounted(struct page *page)
+{
+        return !PageSlab(page) && !PageHeadHuge(page);
+}
+
+/*
+ * This takes a head page as parameter and tells if the
+ * tail page reference counting can be skipped.
+ *
+ * For this to be safe, PageSlab and PageHeadHuge must remain true on
+ * any given page where they return true here, until all tail pins
+ * have been released.
+ */
+static inline bool compound_tail_refcounted(struct page *page)
+{
+        VM_BUG_ON(!PageHead(page));
+        return __compound_tail_refcounted(page);
+}
+
 static inline void get_huge_page_tail(struct page *page)
 {
         /*
          * __split_huge_page_refcount() cannot run
          * from under us.
+         * In turn no need of compound_trans_head here.
          */
         VM_BUG_ON(page_mapcount(page) < 0);
         VM_BUG_ON(atomic_read(&page->_count) != 0);
-        atomic_inc(&page->_mapcount);
+        if (compound_tail_refcounted(compound_head(page)))
+                atomic_inc(&page->_mapcount);
 }
 
 extern bool __get_page_tail(struct page *page);