net: Introduce unregister_netdevice_many()

Introduce rollback_registered_many() and unregister_netdevice_many()

rollback_registered_many() is able to perform necessary steps at device dismantle
time, factorizing two expensive synchronize_net() calls.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 66 insertions, 32 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 0ded0a4768a0..e7c227d7cb98 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1119,6 +1119,7 @@ extern int		dev_queue_xmit(struct sk_buff *skb);
 extern int              register_netdevice(struct net_device *dev);
 extern void             unregister_netdevice_queue(struct net_device *dev,
                                                    struct list_head *head);
+extern void             unregister_netdevice_many(struct list_head *head);
 static inline void unregister_netdevice(struct net_device *dev)
 {
         unregister_netdevice_queue(dev, NULL);
diff --git a/net/core/dev.c b/net/core/dev.c
index ff94e2b8df7f..04d3e3014020 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4637,59 +4637,76 @@ static void net_set_todo(struct net_device *dev)
         list_add_tail(&dev->todo_list, &net_todo_list);
 }
 
-static void rollback_registered(struct net_device *dev)
+static void rollback_registered_many(struct list_head *head)
 {
+        struct net_device *dev;
+
         BUG_ON(dev_boot_phase);
         ASSERT_RTNL();
 
-        /* Some devices call without registering for initialization unwind. */
-        if (dev->reg_state == NETREG_UNINITIALIZED) {
-                printk(KERN_DEBUG "unregister_netdevice: device %s/%p never "
-                                  "was registered\n", dev->name, dev);
+        list_for_each_entry(dev, head, unreg_list) {
+                /* Some devices call without registering
+                 * for initialization unwind.
+                 */
+                if (dev->reg_state == NETREG_UNINITIALIZED) {
+                        pr_debug("unregister_netdevice: device %s/%p never "
+                                 "was registered\n", dev->name, dev);
 
-                WARN_ON(1);
-                return;
-        }
+                        WARN_ON(1);
+                        return;
+                }
 
-        BUG_ON(dev->reg_state != NETREG_REGISTERED);
+                BUG_ON(dev->reg_state != NETREG_REGISTERED);
 
-        /* If device is running, close it first. */
-        dev_close(dev);
+                /* If device is running, close it first. */
+                dev_close(dev);
 
-        /* And unlink it from device chain. */
-        unlist_netdevice(dev);
+                /* And unlink it from device chain. */
+                unlist_netdevice(dev);
 
-        dev->reg_state = NETREG_UNREGISTERING;
+                dev->reg_state = NETREG_UNREGISTERING;
+        }
 
         synchronize_net();
 
-        /* Shutdown queueing discipline. */
-        dev_shutdown(dev);
+        list_for_each_entry(dev, head, unreg_list) {
+                /* Shutdown queueing discipline. */
+                dev_shutdown(dev);
 
 
-        /* Notify protocols, that we are about to destroy
-           this device. They should clean all the things.
-        */
-        call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
+                /* Notify protocols, that we are about to destroy
+                   this device. They should clean all the things.
+                */
+                call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
 
-        /*
-         *      Flush the unicast and multicast chains
-         */
-        dev_unicast_flush(dev);
-        dev_addr_discard(dev);
+                /*
+                 *      Flush the unicast and multicast chains
+                 */
+                dev_unicast_flush(dev);
+                dev_addr_discard(dev);
 
-        if (dev->netdev_ops->ndo_uninit)
-                dev->netdev_ops->ndo_uninit(dev);
+                if (dev->netdev_ops->ndo_uninit)
+                        dev->netdev_ops->ndo_uninit(dev);
 
-        /* Notifier chain MUST detach us from master device. */
-        WARN_ON(dev->master);
+                /* Notifier chain MUST detach us from master device. */
+                WARN_ON(dev->master);
 
-        /* Remove entries from kobject tree */
-        netdev_unregister_kobject(dev);
+                /* Remove entries from kobject tree */
+                netdev_unregister_kobject(dev);
+        }
 
         synchronize_net();
 
-        dev_put(dev);
+        list_for_each_entry(dev, head, unreg_list)
+                dev_put(dev);
+}
+
+static void rollback_registered(struct net_device *dev)
+{
+        LIST_HEAD(single);
+
+        list_add(&dev->unreg_list, &single);
+        rollback_registered_many(&single);
 }
 
 static void __netdev_init_queue_locks_one(struct net_device *dev,
@@ -5272,6 +5289,22 @@ void unregister_netdevice_queue(struct net_device *dev, struct list_head *head)
 EXPORT_SYMBOL(unregister_netdevice_queue);
 
 /**
+ *      unregister_netdevice_many - unregister many devices
+ *      @head: list of devices
+ *
+ */
+void unregister_netdevice_many(struct list_head *head)
+{
+        struct net_device *dev;
+
+        if (!list_empty(head)) {
+                rollback_registered_many(head);
+                list_for_each_entry(dev, head, unreg_list)
+                        net_set_todo(dev);
+        }
+}
+
+/**
  *      unregister_netdev - remove device from the kernel
  *      @dev: device
  *