White smoke that smells of diesel is actually unburnt diesel. This can be caused by low compression (e.g. leaking valves, piston rings or head gasket) or a faulty injector. This may also cause the engine to run roughly and be lower on power.
If the smoke is white with a blue tint to it, then this is burning oil and it has a very distinctive smell. If the engine is actualy using oil (i.e. the level on the dip stick is dropping quickly when you use the car) then it probably is oil smoke. On a turbo diesel lots of burning oil is often caused by failed oil seals within the turbo, and can cause something known as 'runaway' where the engine runs on it's own engine oil. The engine speed in this state will be uncontrollable, and switching off the ignition will not stop the engine.
Either way you need to get the car back to the dealer ASAP.