Re: [libvirt] [PATCH 07/16] snapshot: Add accessors for updating snapshot list relations

On 3/20/19 4:28 PM, John Ferlan wrote: > > > On 3/20/19 1:40 AM, Eric Blake wrote: >> Rather than allowing a leaky abstraction where multiple drivers have >> to open-code operations that update the relations in a >> virDomainSnapshotObjList, it is better to add accessor functions so >> that updates to relations are maintained closer to the internals. The >> goal here is to avoid access to, nchildren, first_child, or sibling >> outside of the lowest level functions, making it easier to refactor >> later on. While many of the conversions are fairly straightforward, >> the MoveChildren refactoring can be a bit interesting to follow. > > Understatement ;-) Some black magic occurs > > The qemuDomainSnapshotReparentChildren "snap->parent = rep->parent" gets > replaced by the new for loop... Tough to see without watching really > closely. > >> +/* Take all children of @from and convert them into children of @to. */ >> +void >> +virDomainSnapshotMoveChildren(virDomainSnapshotObjPtr from, >> + virDomainSnapshotObjPtr to) >> +{ >> + virDomainSnapshotObjPtr child; >> + virDomainSnapshotObjPtr last; >> + >> + for (child = from->first_child; child; child = child->sibling) { >> + child->parent = to; >> + if (!child->sibling) >> + last = child; >> + } >> + to->nchildren += from->nchildren; >> + last->sibling = to->first_child; > > Silly Coverity compiler gets quite confused thinking that @last couldn't > be set while not considering the above loop couldn't end without it > unless of course from->first_child == NULL I suppose, which would be a > different issue. Still if before the for loop we check "if > (!from->first_child) return;", then coverity is happy. Good find from Coverity. If there are no children to move, I do need the early exit, so I'll squash that in.