diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 9080fab1426d09246eb6972347d0708c656d0ae1..017def89e568e0d74c6980462ec94cda3350f405 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -44,6 +44,13 @@ enum {
 #define MPOL_MF_MOVE_ALL (1<<2)	/* Move every page to conform to mapping */
 #define MPOL_MF_INTERNAL (1<<3)	/* Internal flags start here */
 
+/*
+ * Internal flags that share the struct mempolicy flags word with
+ * "mode flags".  These flags are allocated from bit 0 up, as they
+ * are never OR'ed into the mode in mempolicy API arguments.
+ */
+#define MPOL_F_SHARED  (1 << 0)	/* identify shared policies */
+
 #ifdef __KERNEL__
 
 #include <linux/mmzone.h>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 5e7eea2dc8b4d38cac179f1200aa69dcf9f13479..78b18a60b9b22aa44dc2e39504e1cf544080e0ee 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1750,6 +1750,7 @@ static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
 	n->start = start;
 	n->end = end;
 	mpol_get(pol);
+	pol->flags |= MPOL_F_SHARED;	/* for unref */
 	n->policy = pol;
 	return n;
 }