于 2010年11月15日 18:56, Daniel P. Berrange 写道:
On Mon, Nov 15, 2010 at 10:26:22AM +0800, Osier Yang wrote:
Hi, all
Suppose that one updated a domain, and want to restart the domain with original configuration.
However, currently, unless shutdown the domain first, and then restart or reload libvirtd, otherwise domain will still be started with changed configuration. e.g.
# virsh list --all Id Name State ---------------------------------- 1 f14 running
# virsh dumpxml f14 | grep -A 7 cdrom <disk type='file' device='cdrom'> <driver name='qemu' type='raw'/> <source file='/var/lib/libvirt/images/cd1.iso'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' unit='0'/> </disk>
# virsh update-device f14 cd2.xml
# virsh dumpxml f14 | grep -A 7 cdrom <disk type='file' device='cdrom'> <driver name='qemu' type='raw'/> <source file='/var/lib/libvirt/images/cd2.iso'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' unit='0'/> </disk>
# virsh destroy f14 # virsh start f14
# virsh dumpxml f14 | grep -A 7 cdrom <disk type='file' device='cdrom'> <driver name='qemu' type='raw'/> <source file='/var/lib/libvirt/images/cd2.iso'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' unit='0'/> </disk>
it's caused by libvirtd doesn't known if a domain is updated or not, it updated the domain configuration in memory, but client could not known about it.
As a result, one wants to start the domain with original configuration, he has to shutdown the domain first, and then restart libvirt.
This is a bug. libvirt should save a copy of the original configuration at the time the guest starts, so any live changes only remain for the duration of that boot and automatically revert at shutdown.
yeah, I'm tring to fix it.. :-) IMHO it's waste of some memory to let libvirtd save a copy of the original domain configuration, though it could just save the copy only when updating happens. My thought is to export APIs to work around it, the patches is to export API "virDomainIsUpdated", however, think also need another API, which is to update the hash entry of the domain configuration, need to invoke "virHashUpdateEntry". This API could be invoked when starting a updated domain. It reloads the persistent domain configuration and updates the updated domain configuration maintained by libvirtd. How about naming it as "virDomainUpdateConfig"? The diffrence with your thought is that it will really relys on client, reducing the work load of libvirt, but all the clients that using libvirt should be updated with the new APIs to fix the bug then, so, not sure if it's fine. Thanks - Osier
Regards, Daniel