Block IO safety patch for live migration. Xend checks that VBDs are destroyed before unpausing the domain.

tools/python/xen/xend/XendCheckpoint.py

@@ -161,10 +161,12 @@ def restore(xd, fd):
         if handler.store_mfn is None or handler.console_mfn is None:
             raise XendError('Could not read store/console MFN')
 
+	#Block until src closes connection
+	os.read(fd, 1)
         dominfo.unpause()
-
+        
         dominfo.completeRestore(handler.store_mfn, handler.console_mfn)
-
+        
         return dominfo
     except:
         dominfo.destroy()

tools/python/xen/xend/XendDomain.py

@@ -431,7 +431,8 @@ class XendDomain:
         sock.send("receive\n")
         sock.recv(80)
         XendCheckpoint.save(sock.fileno(), dominfo, True, live, dst)
-
+	dominfo.testDeviceComplete()
+	sock.close()
 
     def domain_save(self, domid, dst):
         """Start saving a domain to file.

tools/python/xen/xend/XendDomainInfo.py

@@ -1494,6 +1494,21 @@ class XendDomainInfo:
             if rc != 0:
                 raise XendError("Device of type '%s' refuses migration." % n)
 
+    def testDeviceComplete(self):
+        """ For Block IO migration safety we must ensure that
+        the device has shutdown correctly, i.e. all blocks are
+        flushed to disk
+        """
+        while True:
+            test = 0
+            for i in self.getDeviceController('vbd').deviceIDs():
+                test = 1
+                log.info("Dev %s still active, looping...", i)
+                time.sleep(0.1)
+                
+            if test == 0:
+                break
+
     def migrateDevices(self, network, dst, step, domName=''):
         """Notify the devices about migration
         """