On Fri, 01 Apr 2011 14:10:18 +0800
Wen Congyang <wency@xxxxxxxxxxxxxx> wrote:
> At 04/01/2011 12:19 PM, KAMEZAWA Hiroyuki Write:
> >>From 229cfc90781bfd7024f79db1aed8bea5963757e3 Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > Date: Thu, 31 Mar 2011 18:52:24 +0900
> > Subject: [PATCHv8 2/4] libvirt/qemu - synchronous update of device definition.
> >
> > At persistent modification of inactive domains, we go several steps as
> > - insert disk to vmdef
> > - assign pci address if necessary
> > - assign controller if necessary
> > - save it to file
>
> Step 2 should be after step 3.
>
yes ;)
> >
> > If failure happens in above sequence, that implies there is inconsistency
> > between XML definition in file and vmdef cached in memory. So, it's better
> > to have some rollback method. Implementing undo in each stage doesn't seem
> > very neat, this patch implements a generic one.
> >
> > This patch adds 3 calls.
> > virDomainTemporalCopyAlloc(vmdef)
> > virDomainTemporalCopySync(orig, copy)
> > virDomainTemporalCopyUndo(orig, copy)
> >
> > CopyAlloc() will create a copy of vmdef, CopySync() is for synchronizing
> > copy and orginal, updating origina., CopyUndo() is for discarding for
> > discarding unnecessary things in copy at failure. With these, vmdef
> > modification can be done in following manner.
> >
> > copy = virDomainTemporalCopyAlloc(orig)
> > ....do update on copy
> > ....save updated data to its file
> > if (error)
> > virDomainTemporalCopyUndo(orig, copy);
> > else
> > virDomainTemporalCopySync(orig, copy) # this never fails.
>
> You only copy arrays in orig. How about copy all from orig to copy?
> And we can introduce a new API virDomainObjAssignPersistentDef() that is
> like the API virDomainObjAssignDef().
>
> So vmdef modification can be done like this:
> copy = virDomainTemporalCopyAlloc(orig)
> ....do update on copy
> if (error) {
> virDomainDefFree(copy);
> } else {
> virDomainObjAssignPersistentDef(vm, copy) # this never fails.
> ....save updated data to its file
> }
>
> We can copy vmdef easily:
> 1. xml = virDomainDefFormat(def, VIR_DOMAIN_XML_WRITE_FLAGS)
> 2. newdef = virDomainDefParseString(caps, xml, VIR_DOMAIN_XML_READ_FLAGS)
>
Hmm, could you explain virDomainObjAssignPersistentDef() ?
I think I should finally support moficication of active domains.
Can I replace the whole vmdef of active domain ?
Thanks,
-Kame
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