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Re: [libvirt] How to avoid the disk still persistent after no persistent hotplug and with restarting libvirtd then.



On 08/22/2011 03:12 AM, Osier Yang wrote:
于 2011年08月20日 01:16, Eric Blake 写道:
On 08/19/2011 08:17 AM, Osier Yang wrote:
Libvirt loads the domain conf from the status file
(/var/run/libvirt/qemu/$dom.xml)
if the domain is running, the problem if one restart libvirtd just after
some changing on the domain conf, and then destroy/start the guest.
libvirt will never known what the original domain conf is then.
(vm->newdef is NULL at this moment, generally libvirt restore the domain
conf
to the original conf (vm->newDef) when destroying and shutdown).

Sounds to me like this is a bug in libvirtd reloading. For a running
persistent guest, libvirt should be looking in two files: both the
running state (/var/run/libvirt/qemu/$dom.xml) and the next-boot state
(/etc/lib/libvirt/qemu/$dom.xml); and if they differ, then assign
vm->newDef to the persistent definition.

Is this too expensive? Need to compare most of the properties of the
domain conf (except the auto-generated info, and some other fixed info
such as domain name, UUID, etc. All other info which could be changed
lively should be compared).

We don't necessarily have to do a comparison. Just blindly parsing in both files is a good enough approach, even in the case where the two files end up not describing any difference in inactive configuration. My main point was that since we track state in two files, we should be restoring two files when libvirtd restarts, but right now we are only restoring one.

--
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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