[PATCH] Add a mechanism to detect block device setup failure

[Murillo Fernandes Bernardes <mfb@br.ibm.com>]

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Hi

The problem is: There is no mechanism to detect block device setup failure

Network devices have the same problem, and are fixed with this too.

I handling this problem in the way suggested by aliguori: 
- hotplug scripts write a "hotplug-status" node on store
- Xend DevController.createDevice() check verify this node and return success 
or throw an exception on failure. 
- If no changes in "hotplug-status" node after DEVICE_CREATE_TIMEOUT seconds 
Xend throw an exception showing the problem with hotplug scripts.

Comments?

Regards

-- 
Murillo Fernandes Bernardes

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diff -r 20d1a79ebe31 tools/examples/block-common.sh
--- a/tools/examples/block-common.sh	Wed Oct 26 15:59:13 2005
+++ b/tools/examples/block-common.sh	Thu Oct 27 20:15:02 2005
@@ -42,10 +42,17 @@
   local major
   local minor
   local pdev
-	
+
   major=$(stat -L -c %t "$1")
   minor=$(stat -L -c %T "$1")
+  
+  if [ -z $major  -o -z $minor ]; then
+    fatal "Backend device does not exist"
+  fi
+  
   pdev=$(printf "0x%02x%02x" "0x$major" "0x$minor")
   xenstore_write "$XENBUS_PATH"/physical-device "$pdev" \
                  "$XENBUS_PATH"/node "$1"
+		 
+  success
 }
diff -r 20d1a79ebe31 tools/examples/vif-bridge
--- a/tools/examples/vif-bridge	Wed Oct 26 15:59:13 2005
+++ b/tools/examples/vif-bridge	Thu Oct 27 20:15:02 2005
@@ -45,6 +45,7 @@
           fatal "brctl addif $bridge $vif failed"
 
         ifconfig "$vif" up || fatal "ifconfig $vif up failed"
+        success
         ;;
     down)
         # vifs are auto-removed from bridge.
@@ -55,3 +56,4 @@
 handle_iptable
 
 log debug "vif-bridge operation for $vif successful."
+
diff -r 20d1a79ebe31 tools/examples/vif-nat
--- a/tools/examples/vif-nat	Wed Oct 26 15:59:13 2005
+++ b/tools/examples/vif-nat	Thu Oct 27 20:15:02 2005
@@ -54,3 +54,5 @@
 ip r ${ipcmd} ${ip} dev ${vif} src ${main_ip}
 
 handle_iptable()
+
+success
diff -r 20d1a79ebe31 tools/examples/vif-route
--- a/tools/examples/vif-route	Wed Oct 26 15:59:13 2005
+++ b/tools/examples/vif-route	Thu Oct 27 20:15:02 2005
@@ -46,3 +46,5 @@
 fi
 
 handle_iptable()
+
+success
diff -r 20d1a79ebe31 tools/examples/xen-hotplug-common.sh
--- a/tools/examples/xen-hotplug-common.sh	Wed Oct 26 15:59:13 2005
+++ b/tools/examples/xen-hotplug-common.sh	Thu Oct 27 20:15:02 2005
@@ -29,8 +29,14 @@
 }
 
 fatal() {
+  xenstore_write "$XENBUS_PATH"/hotplug-status error
   log err "$@"
   exit 1
+}
+
+success() {
+  # Tell DevController that backend is "connected"
+  xenstore_write "$XENBUS_PATH"/hotplug-status connected
 }
 
 xenstore_read() {
diff -r 20d1a79ebe31 tools/python/xen/xend/server/DevController.py
--- a/tools/python/xen/xend/server/DevController.py	Wed Oct 26 15:59:13 2005
+++ b/tools/python/xen/xend/server/DevController.py	Thu Oct 27 20:15:02 2005
@@ -16,12 +16,19 @@
 # Copyright (C) 2005 XenSource Ltd
 #============================================================================
 
+import time
+from threading import Event
 
 from xen.xend import sxp
 from xen.xend.XendError import VmError
 from xen.xend.XendLogging import log
+
 from xen.xend.xenstore.xstransact import xstransact
-
+from xen.xend.xenstore.xswatch import xswatch
+
+DEVICE_CREATE_TIMEOUT = 120
+HOTPLUG_STATUS_NODE = "hotplug-status"
+HOTPLUG_STATUS_ERROR = "error"
 
 class DevController:
     """Abstract base class for a device controller.  Device controllers create
@@ -54,6 +61,18 @@
 
         self.writeDetails(config, devid, back, front)
 
+        status, fn_ret = self.waitForBackend(devid)
+        if status:
+            self.destroyDevice(devid)
+            raise VmError( ("Device %s (%s) could not be connected. "
+                            "Hotplug scripts not working") 
+                            % (devid, self.deviceClass))
+
+        elif fn_ret == HOTPLUG_STATUS_ERROR:
+            self.destroyDevice(devid)
+            raise VmError( ("Device %s (%s) could not be connected. "
+                            "Backend device not found!") 
+                            % (devid, self.deviceClass))
         return devid
 
 
@@ -234,6 +253,29 @@
         xstransact.Write(frontpath, frontDetails)
         xstransact.Write(backpath, backDetails)
 
+    def waitForBackend(self,devid):
+        ev = Event()
+
+        def hotplugStatus():
+            status = self.readBackend(devid, HOTPLUG_STATUS_NODE)
+            if status is not None:
+                watch.xs.unwatch(backpath, watch)
+                hotplugStatus.value = status
+                ev.set()
+
+        hotplugStatus.value = None
+        frontpath = self.frontendPath(devid)
+        backpath = xstransact.Read(frontpath, "backend")
+
+        watch = xswatch(backpath, hotplugStatus)
+
+        ev.wait(DEVICE_CREATE_TIMEOUT)
+        if ev.isSet():
+            return (0, hotplugStatus.value)
+        else:
+            return (-1, hotplugStatus.value)
+
+
 
     def backendPath(self, backdom, devid):
         """@param backdom [XendDomainInfo] The backend domain info."""

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