net: bridge: Extract br_vlan_add_existing()

Extract the code that deals with adding a preexisting VLAN to bridge CPU
port to a separate function. A follow-up patch introduces a need to roll
back operations in this block due to an error, and this split will make
the error-handling code clearer.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_vlan.c

@@ -551,43 +551,54 @@ bool br_should_learn(struct net_bridge_port *p, struct sk_buff *skb, u16 *vid)
 	return false;
 }
 
-/* Must be protected by RTNL.
- * Must be called with vid in range from 1 to 4094 inclusive.
- * changed must be true only if the vlan was created or updated
- */
-int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags, bool *changed)
+static int br_vlan_add_existing(struct net_bridge *br,
+				struct net_bridge_vlan_group *vg,
+				struct net_bridge_vlan *vlan,
+				u16 flags, bool *changed)
 {
-	struct net_bridge_vlan_group *vg;
-	struct net_bridge_vlan *vlan;
-	int ret;
-
-	ASSERT_RTNL();
+	int err;
 
-	*changed = false;
-	vg = br_vlan_group(br);
-	vlan = br_vlan_find(vg, vid);
-	if (vlan) {
 	if (!br_vlan_is_brentry(vlan)) {
 		/* Trying to change flags of non-existent bridge vlan */
 		if (!(flags & BRIDGE_VLAN_INFO_BRENTRY))
 			return -EINVAL;
 		/* It was only kept for port vlans, now make it real */
-			ret = br_fdb_insert(br, NULL, br->dev->dev_addr,
+		err = br_fdb_insert(br, NULL, br->dev->dev_addr,
 				    vlan->vid);
-			if (ret) {
-				br_err(br, "failed insert local address into bridge forwarding table\n");
-				return ret;
+		if (err) {
+			br_err(br, "failed to insert local address into bridge forwarding table\n");
+			return err;
 		}
+
 		refcount_inc(&vlan->refcnt);
 		vlan->flags |= BRIDGE_VLAN_INFO_BRENTRY;
 		vg->num_vlans++;
 		*changed = true;
 	}
+
 	if (__vlan_add_flags(vlan, flags))
 		*changed = true;
 
 	return 0;
-	}
+}
+
+/* Must be protected by RTNL.
+ * Must be called with vid in range from 1 to 4094 inclusive.
+ * changed must be true only if the vlan was created or updated
+ */
+int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags, bool *changed)
+{
+	struct net_bridge_vlan_group *vg;
+	struct net_bridge_vlan *vlan;
+	int ret;
+
+	ASSERT_RTNL();
+
+	*changed = false;
+	vg = br_vlan_group(br);
+	vlan = br_vlan_find(vg, vid);
+	if (vlan)
+		return br_vlan_add_existing(br, vg, vlan, flags, changed);
 
 	vlan = kzalloc(sizeof(*vlan), GFP_KERNEL);
 	if (!vlan)