[libvirt] Implement quorum support.

Hello, I'm implementing quorum in libvirt. I've try to follow this proposal: http://www.redhat.com/archives/libvir-list/2014-May/msg00546.html At this point I've done this: - add all the field need by quorum in _virStorageSource (nBackingStores, threshold). - handle more than one backing store in virStorageSource by adding a function virStorageSourcePushBackingStore - add support of the quorum syntax for the xml parser. so now i have to work on qemuBuildDriveStr But I've a problem: in qemu a child of a quorum is a BlockDriverState, where it's a virStorageSource in libvirt, so a child in qemu contain more information than a backingStore in libvirt(blockinfo, throttle...). I think about several solution for this problem: - I can handle quorum's child differently than backingStore and create a "virDomainDiskDefPtr childs" field in virDomainDiskDef or virStorageSource. - I can change the virStorageSourcePtr backingStore, to virDomainDiskDefPtr backingStore, and move the field to backingStore to virDomainDiskDef. -I can move all the field need by a quorum's child from virStorageSource to virDomainDiskDef. But i don't know which solution is the best for libvirt, how do you think i can handle this problem ? Best regards, Matthias