diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2c551b2..49e693b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2349,6 +2349,9 @@
 
 /*
  * Hugetlb_cow() should be called with page lock of the original hugepage held.
+ * Called with hugetlb_instantiation_mutex held and pte_page locked so we
+ * cannot race with other handlers or page migration.
+ * Keep the pte_same checks anyway to make transition from the mutex easier.
  */
 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pte_t *ptep, pte_t pte,