dev: support deferring device flag change notifications

Split dev_change_flags() into two functions: __dev_change_flags() to
perform the actual changes and __dev_notify_flags() to invoke netdevice
notifiers. This will be used by rtnl_link to defer netlink notifications
until the device has been fully configured.

This changes ordering of some operations, in particular:

- netlink notifications are sent after all changes have been performed.
  As a side effect this surpresses one unnecessary netlink message when
  the IFF_UP and other flags are changed simultaneously.

- The NETDEV_UP/NETDEV_DOWN and NETDEV_CHANGE notifiers are invoked
  after all changes have been performed. Their relative is unchanged.

- net_dmaengine_put() is invoked before the NETDEV_DOWN notifier instead
  of afterwards. This should not make any difference since both RX and TX
  are already shut down at this point.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 104 insertions, 61 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 75332b089529..e5972f7f7e1b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1113,19 +1113,7 @@ void dev_load(struct net *net, const char *name)
 }
 EXPORT_SYMBOL(dev_load);
 
-/**
- *      dev_open        - prepare an interface for use.
- *      @dev:   device to open
- *
- *      Takes a device from down to up state. The device's private open
- *      function is invoked and then the multicast lists are loaded. Finally
- *      the device is moved into the up state and a %NETDEV_UP message is
- *      sent to the netdev notifier chain.
- *
- *      Calling this function on an active interface is a nop. On a failure
- *      a negative errno code is returned.
- */
-int dev_open(struct net_device *dev)
+static int __dev_open(struct net_device *dev)
 {
         const struct net_device_ops *ops = dev->netdev_ops;
         int ret;
@@ -1133,13 +1121,6 @@ int dev_open(struct net_device *dev)
         ASSERT_RTNL();
 
         /*
-         *      Is it already up?
-         */
-
-        if (dev->flags & IFF_UP)
-                return 0;
-
-        /*
          *      Is it even present?
          */
         if (!netif_device_present(dev))
@@ -1187,36 +1168,57 @@ int dev_open(struct net_device *dev)
                  *      Wakeup transmit queue engine
                  */
                 dev_activate(dev);
-
-                /*
-                 *      ... and announce new interface.
-                 */
-                call_netdevice_notifiers(NETDEV_UP, dev);
         }
 
         return ret;
 }
-EXPORT_SYMBOL(dev_open);
 
 /**
- *      dev_close - shutdown an interface.
- *      @dev: device to shutdown
+ *      dev_open        - prepare an interface for use.
+ *      @dev:   device to open
  *
- *      This function moves an active device into down state. A
- *      %NETDEV_GOING_DOWN is sent to the netdev notifier chain. The device
- *      is then deactivated and finally a %NETDEV_DOWN is sent to the notifier
- *      chain.
+ *      Takes a device from down to up state. The device's private open
+ *      function is invoked and then the multicast lists are loaded. Finally
+ *      the device is moved into the up state and a %NETDEV_UP message is
+ *      sent to the netdev notifier chain.
+ *
+ *      Calling this function on an active interface is a nop. On a failure
+ *      a negative errno code is returned.
  */
-int dev_close(struct net_device *dev)
+int dev_open(struct net_device *dev)
+{
+        int ret;
+
+        /*
+         *      Is it already up?
+         */
+        if (dev->flags & IFF_UP)
+                return 0;
+
+        /*
+         *      Open device
+         */
+        ret = __dev_open(dev);
+        if (ret < 0)
+                return ret;
+
+        /*
+         *      ... and announce new interface.
+         */
+        rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
+        call_netdevice_notifiers(NETDEV_UP, dev);
+
+        return ret;
+}
+EXPORT_SYMBOL(dev_open);
+
+static int __dev_close(struct net_device *dev)
 {
         const struct net_device_ops *ops = dev->netdev_ops;
-        ASSERT_RTNL();
 
+        ASSERT_RTNL();
         might_sleep();
 
-        if (!(dev->flags & IFF_UP))
-                return 0;
-
         /*
          *      Tell people we are going down, so that they can
          *      prepare to death, when device is still operating.
@@ -1252,14 +1254,34 @@ int dev_close(struct net_device *dev)
         dev->flags &= ~IFF_UP;
 
         /*
-         * Tell people we are down
+         *      Shutdown NET_DMA
          */
-        call_netdevice_notifiers(NETDEV_DOWN, dev);
+        net_dmaengine_put();
+
+        return 0;
+}
+
+/**
+ *      dev_close - shutdown an interface.
+ *      @dev: device to shutdown
+ *
+ *      This function moves an active device into down state. A
+ *      %NETDEV_GOING_DOWN is sent to the netdev notifier chain. The device
+ *      is then deactivated and finally a %NETDEV_DOWN is sent to the notifier
+ *      chain.
+ */
+int dev_close(struct net_device *dev)
+{
+        if (!(dev->flags & IFF_UP))
+                return 0;
+
+        __dev_close(dev);
 
         /*
-         *      Shutdown NET_DMA
+         * Tell people we are down
          */
-        net_dmaengine_put();
+        rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
+        call_netdevice_notifiers(NETDEV_DOWN, dev);
 
         return 0;
 }
@@ -4299,18 +4321,10 @@ unsigned dev_get_flags(const struct net_device *dev)
 }
 EXPORT_SYMBOL(dev_get_flags);
 
-/**
- *      dev_change_flags - change device settings
- *      @dev: device
- *      @flags: device state flags
- *
- *      Change settings on device based state flags. The flags are
- *      in the userspace exported format.
- */
-int dev_change_flags(struct net_device *dev, unsigned flags)
+int __dev_change_flags(struct net_device *dev, unsigned int flags)
 {
-        int ret, changes;
         int old_flags = dev->flags;
+        int ret;
 
         ASSERT_RTNL();
 
@@ -4341,17 +4355,12 @@ int dev_change_flags(struct net_device *dev, unsigned flags)
 
         ret = 0;
         if ((old_flags ^ flags) & IFF_UP) {     /* Bit is different  ? */
-                ret = ((old_flags & IFF_UP) ? dev_close : dev_open)(dev);
+                ret = ((old_flags & IFF_UP) ? __dev_close : __dev_open)(dev);
 
                 if (!ret)
                         dev_set_rx_mode(dev);
         }
 
-        if (dev->flags & IFF_UP &&
-            ((old_flags ^ dev->flags) & ~(IFF_UP | IFF_PROMISC | IFF_ALLMULTI |
-                                          IFF_VOLATILE)))
-                call_netdevice_notifiers(NETDEV_CHANGE, dev);
-
         if ((flags ^ dev->gflags) & IFF_PROMISC) {
                 int inc = (flags & IFF_PROMISC) ? 1 : -1;
 
@@ -4370,11 +4379,47 @@ int dev_change_flags(struct net_device *dev, unsigned flags)
                 dev_set_allmulti(dev, inc);
         }
 
-        /* Exclude state transition flags, already notified */
-        changes = (old_flags ^ dev->flags) & ~(IFF_UP | IFF_RUNNING);
+        return ret;
+}
+
+void __dev_notify_flags(struct net_device *dev, unsigned int old_flags)
+{
+        unsigned int changes = dev->flags ^ old_flags;
+
+        if (changes & IFF_UP) {
+                if (dev->flags & IFF_UP)
+                        call_netdevice_notifiers(NETDEV_UP, dev);
+                else
+                        call_netdevice_notifiers(NETDEV_DOWN, dev);
+        }
+
+        if (dev->flags & IFF_UP &&
+            (changes & ~(IFF_UP | IFF_PROMISC | IFF_ALLMULTI | IFF_VOLATILE)))
+                call_netdevice_notifiers(NETDEV_CHANGE, dev);
+}
+
+/**
+ *      dev_change_flags - change device settings
+ *      @dev: device
+ *      @flags: device state flags
+ *
+ *      Change settings on device based state flags. The flags are
+ *      in the userspace exported format.
+ */
+int dev_change_flags(struct net_device *dev, unsigned flags)
+{
+        int ret, changes;
+        int old_flags = dev->flags;
+
+        ret = __dev_change_flags(dev, flags);
+        if (ret < 0)
+                return ret;
+
+        changes = old_flags ^ dev->flags;
         if (changes)
                 rtmsg_ifinfo(RTM_NEWLINK, dev, changes);
 
+        __dev_notify_flags(dev, old_flags);
         return ret;
 }
 EXPORT_SYMBOL(dev_change_flags);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 020e43bfef5f..c21ec4236dd0 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1427,8 +1427,6 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
         switch (event) {
         case NETDEV_UP:
         case NETDEV_DOWN:
-                rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
-                break;
         case NETDEV_PRE_UP:
         case NETDEV_POST_INIT:
         case NETDEV_REGISTER: