Ember Mixin actions

I am trying to develop my first mixin. I want my controllers to be able to toggle an editing property and to set it to false when the model is saved or rolled back.

in myapp/mixins/editable.js:

import Ember from "ember";

export default Ember.Mixin.create({
  editing: false,

  actions: {
    toggleEditing: function() {
      this.toggleProperty('editing');
    },
    cancel: function () {
      console.log("editable mixin: cancel");
      this.set('editing', false);
      return true;
    },
    save: function () {
      console.log("editable mixin: save");
      this.set('editing', false);
      return true;
    }
  }
});

I thought this would be great as I can have consistent edit buttons in my templates like this.

in myapp/templates/sometemplate.hbs:

{{#if editing}}
  {{#if model.isDirty}}
    <button class="action-icon" {{action "cancel"}}>{{fa-icon "times" title="discard changes"}}</button>
    <button class="action-icon" {{action "save"}}>{{fa-icon "save" title="save changes"}}</button>
  {{else}}
    <button class="action-icon" {{action "toggleEditing"}}>{{fa-icon "times" title="cancel"}}</button>
  {{/if}}
{{else}}
  <button class="action-icon" {{action "toggleEditing"}}>{{fa-icon "pencil" title="edit"}}</button>
{{/if}}

...and I can control saving and cancelling in my route, something like this:

in myapp/route/someroute.js:

import Ember from "ember";

export default Ember.Route.extend({
  model: function(params) {
    return this.store.find('somemodel', params.model_id);
  },
  actions: {
    save: function () {
      console.log("route: save");
      this.modelFor('somemodel').save();
    },
    cancel: function () {
      console.log("route: cancel");
      this.modelFor('somemodel').rollback();
    },
  }
});

However, I am now confused... what happens if the save fails? How can I plumb it together so that the editing property is set to false only when the save has successfully completed?

Is there some way to access a promise from an action on the route? Am I heading in the right direction with this?