xen-netback: Handle backend state transitions in a more robust way
When the frontend state changes netback now specifies its desired state to
a new function, set_backend_state(), which transitions through any
necessary intermediate states.
This fixes an issue observed with some old Windows frontend drivers where
they failed to transition through the Closing state and netback would not
behave correctly.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index a53782e..b45bce2 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;
@@ -136,6 +142,8 @@
if (err)
goto fail;
+ be->state = XenbusStateInitWait;
+
/* This kicks hotplug scripts, so do it immediately. */
backend_create_xenvif(be);
@@ -208,24 +216,113 @@
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 +334,33 @@
{
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 +453,9 @@
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 +485,8 @@
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);
}
