[PATCH net-next v8 2/5] net: add a generation counter for dev->mc changes

@@ -256,6 +256,11 @@ struct netdev_hw_addr_list {
 
 	/* Auxiliary tree for faster lookup on addition and deletion */
 	struct rb_root		tree;
+
+	/* The device a list belongs to, NULL for snapshots and other
+	 * standalone lists
+	 */
+	struct net_device	*owner;
 };
 
 #define netdev_hw_addr_list_count(l) ((l)->count)

@@ -71,6 +71,7 @@ struct net {
 	spinlock_t		rules_mod_lock;
 
 	unsigned int		dev_base_seq;	/* protected by rtnl_mutex */
+	atomic_t		dev_mc_genid;	/* bumped on dev->mc changes */
 	u32			ifindex;
 
 	spinlock_t		nsid_lock;

@@ -16,6 +16,37 @@
 
 #include "dev.h"
 
+/* Only dev->mc is tracked, RTM_GETMULTICAST dumps use the netns generation
+ * counter to detect changes between dump rounds.
+ */
+static void __hw_addr_changed(struct netdev_hw_addr_list *list)
+{
+	struct net_device *dev = list->owner;
+
+	if (dev && list == &dev->mc)
+		atomic_inc(&dev_net(dev)->dev_mc_genid);
+}
+
+static void __hw_addr_count_inc(struct netdev_hw_addr_list *list)
+{
+	list->count++;
+	__hw_addr_changed(list);
+}
+
+static void __hw_addr_count_dec(struct netdev_hw_addr_list *list)
+{
+	list->count--;
+	__hw_addr_changed(list);
+}
+
+static void __hw_addr_count_reset(struct netdev_hw_addr_list *list)
+{
+	if (!list->count)
+		return;
+	list->count = 0;
+	__hw_addr_changed(list);
+}
+
 /*
  * General list handling functions
  */

@@ -125,7 +156,7 @@ static int __hw_addr_add_ex(struct netdev_hw_addr_list *list,
 	rb_insert_color(&ha->node, &list->tree);
 
 	list_add_tail_rcu(&ha->list, &list->list);
-	list->count++;
+	__hw_addr_count_inc(list);
 
 	return 0;
 }

@@ -161,7 +192,7 @@ static int __hw_addr_del_entry(struct netdev_hw_addr_list *list,
 
 	list_del_rcu(&ha->list);
 	kfree_rcu(ha, rcu_head);
-	list->count--;
+	__hw_addr_count_dec(list);
 	return 0;
 }
 

@@ -492,7 +523,7 @@ void __hw_addr_flush(struct netdev_hw_addr_list *list)
 		list_del_rcu(&ha->list);
 		kfree_rcu(ha, rcu_head);
 	}
-	list->count = 0;
+	__hw_addr_count_reset(list);
 }
 EXPORT_SYMBOL_IF_KUNIT(__hw_addr_flush);
 

@@ -501,6 +532,7 @@ void __hw_addr_init(struct netdev_hw_addr_list *list)
 	INIT_LIST_HEAD(&list->list);
 	list->count = 0;
 	list->tree = RB_ROOT;
+	list->owner = NULL;
 }
 EXPORT_SYMBOL(__hw_addr_init);
 

@@ -536,7 +568,7 @@ int __hw_addr_list_snapshot(struct netdev_hw_addr_list *snap,
 			entry = list_first_entry(&cache->list,
 						 struct netdev_hw_addr, list);
 			list_del(&entry->list);
-			cache->count--;
+			__hw_addr_count_dec(cache);
 			memcpy(entry->addr, ha->addr, addr_len);
 			entry->type = ha->type;
 			entry->global_use = false;

@@ -554,7 +586,7 @@ int __hw_addr_list_snapshot(struct netdev_hw_addr_list *snap,
 
 		list_add_tail(&entry->list, &snap->list);
 		__hw_addr_insert(snap, entry, addr_len);
-		snap->count++;
+		__hw_addr_count_inc(snap);
 	}
 
 	return 0;

@@ -604,14 +636,14 @@ void __hw_addr_list_reconcile(struct netdev_hw_addr_list *real_list,
 			if (delta > 0) {
 				rb_erase(&ref_ha->node, &ref->tree);
 				list_del(&ref_ha->list);
-				ref->count--;
+				__hw_addr_count_dec(ref);
 				ref_ha->sync_cnt = delta;
 				ref_ha->refcount = delta;
 				list_add_tail_rcu(&ref_ha->list,
 						  &real_list->list);
 				__hw_addr_insert(real_list, ref_ha,
 						 addr_len);
-				real_list->count++;
+				__hw_addr_count_inc(real_list);
 			}
 			continue;
 		}

@@ -622,7 +654,7 @@ void __hw_addr_list_reconcile(struct netdev_hw_addr_list *real_list,
 			rb_erase(&real_ha->node, &real_list->tree);
 			list_del_rcu(&real_ha->list);
 			kfree_rcu(real_ha, rcu_head);
-			real_list->count--;
+			__hw_addr_count_dec(real_list);
 		}
 	}
 

@@ -685,6 +717,7 @@ int dev_addr_init(struct net_device *dev)
 	/* rtnl_mutex must be held here */
 
 	__hw_addr_init(&dev->dev_addrs);
+	dev->dev_addrs.owner = dev;
 	memset(addr, 0, sizeof(addr));
 	err = __hw_addr_add(&dev->dev_addrs, addr, sizeof(addr),
 			    NETDEV_HW_ADDR_T_LAN);

@@ -962,6 +995,7 @@ EXPORT_SYMBOL(dev_uc_flush);
 void dev_uc_init(struct net_device *dev)
 {
 	__hw_addr_init(&dev->uc);
+	dev->uc.owner = dev;
 }
 EXPORT_SYMBOL(dev_uc_init);
 

@@ -1177,6 +1211,7 @@ EXPORT_SYMBOL(dev_mc_flush);
 void dev_mc_init(struct net_device *dev)
 {
 	__hw_addr_init(&dev->mc);
+	dev->mc.owner = dev;
 }
 EXPORT_SYMBOL(dev_mc_init);
 

@@ -1348,6 +1383,7 @@ static void netif_rx_mode_retry(struct timer_list *t)
 void netif_rx_mode_init(struct net_device *dev)
 {
 	__hw_addr_init(&dev->rx_mode_addr_cache);
+	dev->rx_mode_addr_cache.owner = dev;
 	timer_setup(&dev->rx_mode_retry_timer, netif_rx_mode_retry, 0);
 }