Re: [Xen-devel] [PATCH] xend: fix vbd/tapdisk device destruction

[Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>]

Hi Ryan,

I detected problems by testing your patch.

In the case of inactive domains:
xm block-detach failed.

 # xm block-list vm2
 Vdev  BE handle state evt-ch ring-ref BE-path
 769    -1   0     -1     -1     -1    ??
 833    -1   0     -1     -1     -1    ??
 # xm block-detach vm2 833
 Error: (22, 'Invalid argument')
 Usage: xm block-detach <Domain> <DevId> [-f|--force]
 
 Destroy a domain's virtual block device

In the case of active domains:
xm block-deatch succeeded. But I saw the following message in 
xend.log.

 # xm block-list vm2
 Vdev  BE handle state evt-ch ring-ref BE-path
 769    0    0     4      10     8     /local/domain/0/backend/vbd/3/769  
 833    0    0     4      11     9     /local/domain/0/backend/vbd/3/833  
 # xm block-detach vm2 833
 # xm block-list vm2
 Vdev  BE handle state evt-ch ring-ref BE-path
 769    0    0     4      10     8     /local/domain/0/backend/vbd/3/769  

 [2009-06-24 12:49:00 4433] DEBUG (XendDomainInfo:1268) error reading backend 
for device (833): 


To solve all problems, I will send a patch instead of your patch.

Best regards,
 Kan

Tue, 23 Jun 2009 10:10:39 -0700, "Ryan O'Connor" wrote:

>blktap2 devices attach as a regular 'vbd' rather than a 'tap' device.
>Accordingly, Xend should use 'vbd' as the device class of blktap2 devices. 
>This
>patch determines the appropriate device class by reading the 'type' field 
>of the
>backend's xenstore entry.
>
>Signed-off-by: Ryan O'Connor <rjo@xxxxxxxxx>
>
>diff -r 3c7536d6b583 -r 3f100fc620fd tools/python/xen/xend/XendDomainInfo.py
>--- a/tools/python/xen/xend/XendDomainInfo.py  Tue Jun 23 17:27:01 2009 +0100
>+++ b/tools/python/xen/xend/XendDomainInfo.py  Tue Jun 23 10:09:20 2009 -0700
>@@ -1244,13 +1244,33 @@ class XendDomainInfo:
>                     dev_num += 1
>             return sxprs
> 
>-    def getBlockDeviceClass(self, devid):
>-        # To get a device number from the devid,
>-        # we temporarily use the device controller of VBD.
>-        dev = self.getDeviceController('vbd').convertToDeviceNumber(devid)
>-        dev_info = self._getDeviceInfo_vbd(dev)
>-        if dev_info:
>-            return dev_info[0]
>+    def getBlockDeviceClass(self, devid, deviceClass=False):
>+        backendType = 'vbd'
>+
>+        # For backwards compatability, we may have to get deviceClass 
>ourselves
>+        if not deviceClass:
>+            t = xstransact("%s/device" % self.dompath)
>+            for devclass in XendDevices.valid_devices():
>+                if devid in t.list(devclass):
>+                    deviceClass = devclass
>+                    break
>+            t.abort()
>+
>+        try:
>+            # Note: deviceClass may be incorrect, so we cannot trust 
>readBackend
>+            # or readFrontend from the Device Controller to succeed
>+            backendPath = xstransact.Read("%s/device/%s/%s"
>+                                          % (self.dompath, deviceClass, 
>devid),
>+                                          "backend")
>+            backendType = xstransact.Read(backendPath, "type")
>+        except Exception, ex:
>+            # we can probably just assume the block device is a VBD
>+            log.debug("error reading backend for device (%s): %s", devid, 
>str(ex))
>+
>+        if backendType == 'tap':
>+            return 'tap'
>+        else:
>+            return 'vbd'
> 
>     def _getDeviceInfo_vif(self, mac):
>         for dev_type, dev_info in self.info.all_devices_sxpr():
>@@ -2217,7 +2237,7 @@ class XendDomainInfo:
>                             # may possibly be "tap". Just in case, verify
>                             # device class.
>                             devid = dev.split('/')[-1]
>-                            true_devclass = self.getBlockDeviceClass(devid)
>+                            true_devclass = self.getBlockDeviceClass(devid
>, devclass)
>                         log.debug("Removing %s", dev);
>                         self.destroyDevice(true_devclass, dev, False);
>                     except:
>
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