1 files changed, 14 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index 8acb936..6d1f920 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -407,6 +407,20 @@ struct address_space *page_mapping(struct page *page)
 	return mapping;
 }
 
+/* Slow path of page_mapcount() for compound pages */
+int __page_mapcount(struct page *page)
+{
+	int ret;
+
+	ret = atomic_read(&page->_mapcount) + 1;
+	page = compound_head(page);
+	ret += atomic_read(compound_mapcount_ptr(page)) + 1;
+	if (PageDoubleMap(page))
+		ret--;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__page_mapcount);
+
 int overcommit_ratio_handler(struct ctl_table *table, int write,
 			     void __user *buffer, size_t *lenp,
 			     loff_t *ppos)