IPoIB: clarify to_ipoib_neigh()

Cosmetic change: make alignment explicit in to_ipoib_neigh.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -217,10 +217,16 @@ struct ipoib_neigh {
 	struct list_head    list;
 };
 
+/*
+ * We stash a pointer to our private neighbour information after our
+ * hardware address in neigh->ha.  The ALIGN() expression here makes
+ * sure that this pointer is stored aligned so that an unaligned
+ * load is not needed to dereference it.
+ */
 static inline struct ipoib_neigh **to_ipoib_neigh(struct neighbour *neigh)
 {
-	return (struct ipoib_neigh **) (neigh->ha + 24 -
-					(offsetof(struct neighbour, ha) & 4));
+	return (void*) neigh + ALIGN(offsetof(struct neighbour, ha) +
+				     INFINIBAND_ALEN, sizeof(void *));
 }
 
 extern struct workqueue_struct *ipoib_workqueue;