diff --git a/mm/internal.h b/mm/internal.h
index aee4761..5307a02 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -342,3 +342,7 @@
 extern u64 hwpoison_filter_flags_value;
 extern u64 hwpoison_filter_memcg;
 extern u32 hwpoison_filter_enable;
+
+extern unsigned long vm_mmap_pgoff(struct file *, unsigned long,
+        unsigned long, unsigned long,
+        unsigned long, unsigned long);