1 files changed, 20 insertions, 4 deletions

diff --git a/mm/util.c b/mm/util.c
index 2d28f7930043..6d1f9200f74e 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -386,7 +386,9 @@ struct anon_vma *page_anon_vma(struct page *page)
 
 struct address_space *page_mapping(struct page *page)
 {
-        unsigned long mapping;
+        struct address_space *mapping;
+
+        page = compound_head(page);
 
         /* This happens if someone calls flush_dcache_page on slab page */
         if (unlikely(PageSlab(page)))
@@ -399,11 +401,25 @@ struct address_space *page_mapping(struct page *page)
                 return swap_address_space(entry);
         }
 
-        mapping = (unsigned long)page->mapping;
-        if (mapping & PAGE_MAPPING_FLAGS)
+        mapping = page->mapping;
+        if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
                 return NULL;
-        return page->mapping;
+        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,