Re: [libvirt] RFC: add new API to known if domain has been updated

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.

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.