bonding: convert first/last slave logic to use neighbours

For that, use netdev_adjacent_get_private(list_head) on bond's lower
neighbour list members. Also, add a small macro - bond_slave_list(bond),
which returns the bond list via neighbour list.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bonding/bonding.h

@@ -72,19 +72,24 @@
 	res; })
 
 /* slave list primitives */
-#define bond_has_slaves(bond) !list_empty(&(bond)->dev->adj_list.lower)
+#define bond_slave_list(bond) (&(bond)->dev->adj_list.lower)
+
+#define bond_has_slaves(bond) !list_empty(bond_slave_list(bond))
 
 #define bond_to_slave(ptr) list_entry(ptr, struct slave, list)
 
 /* IMPORTANT: bond_first/last_slave can return NULL in case of an empty list */
 #define bond_first_slave(bond) \
-	list_first_entry_or_null(&(bond)->slave_list, struct slave, list)
+	(bond_has_slaves(bond) ? \
+		netdev_adjacent_get_private(bond_slave_list(bond)->next) : \
+		NULL)
 #define bond_last_slave(bond) \
-	(list_empty(&(bond)->slave_list) ? NULL : \
-					   bond_to_slave((bond)->slave_list.prev))
+	(bond_has_slaves(bond) ? \
+		netdev_adjacent_get_private(bond_slave_list(bond)->prev) : \
+		NULL)
 
-#define bond_is_first_slave(bond, pos) ((pos)->list.prev == &(bond)->slave_list)
-#define bond_is_last_slave(bond, pos) ((pos)->list.next == &(bond)->slave_list)
+#define bond_is_first_slave(bond, pos) (pos == bond_first_slave(bond))
+#define bond_is_last_slave(bond, pos) (pos == bond_last_slave(bond))
 
 /* Since bond_first/last_slave can return NULL, these can return NULL too */
 #define bond_next_slave(bond, pos) \