[Xen-devel] [PATCH]restore name/uuid uniqueness check

[Zhigang Wang <zhigang.x.wang@xxxxxxxxxx>]

hi all,

currently, if I restore a vm when the vm is running, it will cause two running
vms with the same name/uuid (the second vm is not functional due to disk image
in use).

# xm create OVM_EL5U1_X86_64_PVM_4GB
# xm list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0   543     2     r-----    400.1
OVM_EL5U1_X86_64_PVM_4GB                     3   128     1     -b----     14.2
# xm save 3 /tmp/s1
# xm create OVM_EL5U1_X86_64_PVM_4GB
# xm restore /tmp/s1
# xm list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0   543     2     r-----    411.6
OVM_EL5U1_X86_64_PVM_4GB                     4   128     1     -b----     15.3
OVM_EL5U1_X86_64_PVM_4GB                     5   128     1     -b----      0.7
# xm log
--snip--
[2008-01-23 05:13:57 2502] DEBUG (DevController:603) hotplugStatusCallback 5.
[2008-01-23 05:13:57 2502] ERROR (XendCheckpoint:286) Device 768 (vbd) could 
not be connected.
File /share/vm/OVM_EL5U1_X86_64_PVM_4GB/system.img is loopback-mounted through 
/dev/loop0,
which is mounted in a guest domain,
and so cannot be mounted now.
Traceback (most recent call last):
 File "/usr/lib/python2.4/site-packages/xen/xend/XendCheckpoint.py", line 284, 
in restore
   dominfo.waitForDevices() # Wait for backends to set up
 File "/usr/lib/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 565, 
in waitForDevices
   self.getDeviceController(devclass).waitForDevices()
 File "/usr/lib/python2.4/site-packages/xen/xend/server/DevController.py", line 
151, in waitForDevices
   return map(self.waitForDevice, self.deviceIDs())
 File "/usr/lib/python2.4/site-packages/xen/xend/server/DevController.py", line 
186, in waitForDevice
   raise VmError("Device %s (%s) could not be connected.\n%s" %
VmError: Device 768 (vbd) could not be connected.
File /share/vm/OVM_EL5U1_X86_64_PVM_4GB/system.img is loopback-mounted through 
/dev/loop0,
which is mounted in a guest domain,
and so cannot be mounted now.
--snip--

if set the disk emulation mode to 'w!', both vms will be functional, but the
filesystem will crash soon.

local live migration has this issue two.

this patch makes name/uuid uniqueness check when restore. but it will disable
local migration.

please give some advice on resolving this problem while don't break local
migration. if cannot find one, I prefer disable local migration.

thanks,

zhigang

--- xen-3.1.2.orig/tools/python/xen/xend/XendCheckpoint.py      2008-01-15 
19:19:14.000000000 +0800
+++ xen-3.1.2/tools/python/xen/xend/XendCheckpoint.py   2008-01-22 
13:27:21.000000000 +0800
@@ -170,6 +170,13 @@ def restore(xd, fd, dominfo = None, paus
 
     vmconfig = p.get_val()
 
+    domconfig = XendConfig(sxp_obj = vmconfig)
+    othervm = xd.domain_lookup_nr(domconfig["name_label"])
+    if othervm is None or othervm.domid is None:
+        othervm = xd.domain_lookup_nr(domconfig["uuid"])
+    if othervm is not None and othervm.domid is not None: 
+        raise VmError("Domain '%s' already exists with ID '%d'" % 
(domconfig["name_label"], othervm.domid))
+
     if dominfo:
         dominfo.resume()
     else:

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