Xen devel - Jan 2008 - [PATCH]restore name/uuid uniqueness check

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



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On 23/1/08 06:59, "Zhigang Wang" <zhigang.x.wang@oracle.com>
wrote:
> 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.
Since local migration is the sum total of our automated per-changeset
testing of migration, disabling it is not going to happen.

Perhaps you can disable your uniqueness checks on migration?

 -- Keir



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On 23/1/08 08:07, "Keir Fraser" <Keir.Fraser@cl.cam.ac.uk>
wrote:
> Perhaps you can disable your uniqueness checks on migration?
This is quite sensible actually, because a migration does not create or
restart a new domain. It just relocates an already-running domain, to which
uniqueness checks should already have been applied.

 -- Keir



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hi
  I read the code of xc_domain_save(), and i am confused about the 
function of     analysis_phase(xc_handle, dom, p2m_size, to_skip, 0) ,  
what work does it do ?
  could someone give me a help?

Thanks in advance


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Keir Fraser wrote:
> 
> 
> On 23/1/08 08:07, "Keir Fraser" <Keir.Fraser@cl.cam.ac.uk>
wrote:
> 
>> Perhaps you can disable your uniqueness checks on migration?
> 
> This is quite sensible actually, because a migration does not create or
> restart a new domain. It just relocates an already-running domain, to which
> uniqueness checks should already have been applied.
> 
>  -- Keir
this is a revised patch. I disable the uniqueness check by adding a extra
parameter to domain_restore_fd.

have tested on xen-3.1-testing.

regards,

zhigang


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