1 files changed, 122 insertions, 30 deletions

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index a53782ef1540..1b08d8798372 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -24,6 +24,12 @@
 struct backend_info {
         struct xenbus_device *dev;
         struct xenvif *vif;
+
+        /* This is the state that will be reflected in xenstore when any
+         * active hotplug script completes.
+         */
+        enum xenbus_state state;
+
         enum xenbus_state frontend_state;
         struct xenbus_watch hotplug_status_watch;
         u8 have_hotplug_status_watch:1;
@@ -33,11 +39,15 @@ static int connect_rings(struct backend_info *);
 static void connect(struct backend_info *);
 static void backend_create_xenvif(struct backend_info *be);
 static void unregister_hotplug_status_watch(struct backend_info *be);
+static void set_backend_state(struct backend_info *be,
+                              enum xenbus_state state);
 
 static int netback_remove(struct xenbus_device *dev)
 {
         struct backend_info *be = dev_get_drvdata(&dev->dev);
 
+        set_backend_state(be, XenbusStateClosed);
+
         unregister_hotplug_status_watch(be);
         if (be->vif) {
                 kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
@@ -136,6 +146,8 @@ static int netback_probe(struct xenbus_device *dev,
         if (err)
                 goto fail;
 
+        be->state = XenbusStateInitWait;
+
         /* This kicks hotplug scripts, so do it immediately. */
         backend_create_xenvif(be);
 
@@ -208,24 +220,113 @@ static void backend_create_xenvif(struct backend_info *be)
         kobject_uevent(&dev->dev.kobj, KOBJ_ONLINE);
 }
 
-
-static void disconnect_backend(struct xenbus_device *dev)
+static void backend_disconnect(struct backend_info *be)
 {
-        struct backend_info *be = dev_get_drvdata(&dev->dev);
-
         if (be->vif)
                 xenvif_disconnect(be->vif);
 }
 
-static void destroy_backend(struct xenbus_device *dev)
+static void backend_connect(struct backend_info *be)
 {
-        struct backend_info *be = dev_get_drvdata(&dev->dev);
+        if (be->vif)
+                connect(be);
+}
 
-        if (be->vif) {
-                kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
-                xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
-                xenvif_free(be->vif);
-                be->vif = NULL;
+static inline void backend_switch_state(struct backend_info *be,
+                                        enum xenbus_state state)
+{
+        struct xenbus_device *dev = be->dev;
+
+        pr_debug("%s -> %s\n", dev->nodename, xenbus_strstate(state));
+        be->state = state;
+
+        /* If we are waiting for a hotplug script then defer the
+         * actual xenbus state change.
+         */
+        if (!be->have_hotplug_status_watch)
+                xenbus_switch_state(dev, state);
+}
+
+/* Handle backend state transitions:
+ *
+ * The backend state starts in InitWait and the following transitions are
+ * allowed.
+ *
+ * InitWait -> Connected
+ *
+ *    ^    \         |
+ *    |     \        |
+ *    |      \       |
+ *    |       \      |
+ *    |        \     |
+ *    |         \    |
+ *    |          V   V
+ *
+ *  Closed  <-> Closing
+ *
+ * The state argument specifies the eventual state of the backend and the
+ * function transitions to that state via the shortest path.
+ */
+static void set_backend_state(struct backend_info *be,
+                              enum xenbus_state state)
+{
+        while (be->state != state) {
+                switch (be->state) {
+                case XenbusStateClosed:
+                        switch (state) {
+                        case XenbusStateInitWait:
+                        case XenbusStateConnected:
+                                pr_info("%s: prepare for reconnect\n",
+                                        be->dev->nodename);
+                                backend_switch_state(be, XenbusStateInitWait);
+                                break;
+                        case XenbusStateClosing:
+                                backend_switch_state(be, XenbusStateClosing);
+                                break;
+                        default:
+                                BUG();
+                        }
+                        break;
+                case XenbusStateInitWait:
+                        switch (state) {
+                        case XenbusStateConnected:
+                                backend_connect(be);
+                                backend_switch_state(be, XenbusStateConnected);
+                                break;
+                        case XenbusStateClosing:
+                        case XenbusStateClosed:
+                                backend_switch_state(be, XenbusStateClosing);
+                                break;
+                        default:
+                                BUG();
+                        }
+                        break;
+                case XenbusStateConnected:
+                        switch (state) {
+                        case XenbusStateInitWait:
+                        case XenbusStateClosing:
+                        case XenbusStateClosed:
+                                backend_disconnect(be);
+                                backend_switch_state(be, XenbusStateClosing);
+                                break;
+                        default:
+                                BUG();
+                        }
+                        break;
+                case XenbusStateClosing:
+                        switch (state) {
+                        case XenbusStateInitWait:
+                        case XenbusStateConnected:
+                        case XenbusStateClosed:
+                                backend_switch_state(be, XenbusStateClosed);
+                                break;
+                        default:
+                                BUG();
+                        }
+                        break;
+                default:
+                        BUG();
+                }
         }
 }
 
@@ -237,40 +338,33 @@ static void frontend_changed(struct xenbus_device *dev,
 {
         struct backend_info *be = dev_get_drvdata(&dev->dev);
 
-        pr_debug("frontend state %s\n", xenbus_strstate(frontend_state));
+        pr_debug("%s -> %s\n", dev->otherend, xenbus_strstate(frontend_state));
 
         be->frontend_state = frontend_state;
 
         switch (frontend_state) {
         case XenbusStateInitialising:
-                if (dev->state == XenbusStateClosed) {
-                        pr_info("%s: prepare for reconnect\n", dev->nodename);
-                        xenbus_switch_state(dev, XenbusStateInitWait);
-                }
+                set_backend_state(be, XenbusStateInitWait);
                 break;
 
         case XenbusStateInitialised:
                 break;
 
         case XenbusStateConnected:
-                if (dev->state == XenbusStateConnected)
-                        break;
-                if (be->vif)
-                        connect(be);
+                set_backend_state(be, XenbusStateConnected);
                 break;
 
         case XenbusStateClosing:
-                disconnect_backend(dev);
-                xenbus_switch_state(dev, XenbusStateClosing);
+                set_backend_state(be, XenbusStateClosing);
                 break;
 
         case XenbusStateClosed:
-                xenbus_switch_state(dev, XenbusStateClosed);
+                set_backend_state(be, XenbusStateClosed);
                 if (xenbus_dev_is_online(dev))
                         break;
-                destroy_backend(dev);
                 /* fall through if not online */
         case XenbusStateUnknown:
+                set_backend_state(be, XenbusStateClosed);
                 device_unregister(&dev->dev);
                 break;
 
@@ -363,7 +457,9 @@ static void hotplug_status_changed(struct xenbus_watch *watch,
         if (IS_ERR(str))
                 return;
         if (len == sizeof("connected")-1 && !memcmp(str, "connected", len)) {
-                xenbus_switch_state(be->dev, XenbusStateConnected);
+                /* Complete any pending state change */
+                xenbus_switch_state(be->dev, be->state);
+
                 /* Not interested in this watch anymore. */
                 unregister_hotplug_status_watch(be);
         }
@@ -393,12 +489,8 @@ static void connect(struct backend_info *be)
         err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch,
                                    hotplug_status_changed,
                                    "%s/%s", dev->nodename, "hotplug-status");
-        if (err) {
-                /* Switch now, since we can't do a watch. */
-                xenbus_switch_state(dev, XenbusStateConnected);
-        } else {
+        if (!err)
                 be->have_hotplug_status_watch = 1;
-        }
 
         netif_wake_queue(be->vif->dev);
 }