Re: [RFC v2] migration: Add migrate-set-bitmap-node-mapping

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Max Reitz (mreitz@redhat.com) wrote:

<snip>

> +void qmp_migrate_set_bitmap_node_mapping(MigrationBlockNodeMappingList *mapping,
> +                                         Error **errp)
> +{
> +    QDict *in_mapping = qdict_new();
> +    QDict *out_mapping = qdict_new();
> +
> +    for (; mapping; mapping = mapping->next) {
> +        MigrationBlockNodeMapping *entry = mapping->value;
> +
> +        if (qdict_haskey(out_mapping, entry->node_name)) {
> +            error_setg(errp, "Cannot map node name '%s' twice",
> +                       entry->node_name);
> +            goto fail;
> +        }

I'm not too clear exactly which case this is protecting against;
I think that's protecting against mapping

  'src1'->'dst1' and 'src1'->'dst2'
which is a good check.s (or maybe it's checking against dst2 twice?)

What about cases where there is no mapping - e.g. imagine
that we have b1/b2 on the source and b2/b3 on the dest; now
if we add just a mapping:

  b1->b2

then we end up with:

  b1 -> b2
  b2 -> b2  (non-mapped)
        b3

so we have a clash there - are we protected against that?

Dave

> +        if (qdict_haskey(in_mapping, entry->alias)) {
> +            error_setg(errp, "Cannot use alias '%s' twice",
> +                       entry->alias);
> +            goto fail;
> +        }
> +
> +        qdict_put_str(in_mapping, entry->alias, entry->node_name);
> +        qdict_put_str(out_mapping, entry->node_name, entry->alias);
> +    }
> +
> +    qobject_unref(dirty_bitmap_mig_state.node_in_mapping);
> +    qobject_unref(dirty_bitmap_mig_state.node_out_mapping);
> +
> +    dirty_bitmap_mig_state.node_in_mapping = in_mapping;
> +    dirty_bitmap_mig_state.node_out_mapping = out_mapping;
> +
> +    return;
> +
> +fail:
> +    qobject_unref(in_mapping);
> +    qobject_unref(out_mapping);
> +}
> +
>  static SaveVMHandlers savevm_dirty_bitmap_handlers = {
>      .save_setup = dirty_bitmap_save_setup,
>      .save_live_complete_postcopy = dirty_bitmap_save_complete,
> -- 
> 2.26.2
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK