Knocking 2.8 GU

Hi All,

Got back last night from leaving my baby at a friends house due to possible engine
damage. Was driving up to Sunshine Coast last night when I heard this very
faint knocking coming from engine bay. It gradually grew louder over the
coarse of 5 km so I pulled over and confirmed it was definitely an engine
knock as it kept doing it whilst stationary and idling then increased in
tempo when revving the engine. I checked everywhere under the bonnet to see
if it was the fan hitting the shroud, broken belt etc and found the knock is
very prominent in the top of the engine confirmed from front and both sides.
I was in the middle of nowhere so proceeded at 80km/h to Maroochydore turn
off (a few km away). During this I noticed a lot of smoke coming from the
rear so pulled over again. Engine will not idle at the usually 750 - 800rpm
but instead around the 550-600rpm mark. Also quite sluggish at low rpm's.
Noise is extremely loud now. I rang a friend who has the same car as me who
listened to the noise and instantly said big end bearing failure but this
did not explain the exhaust smoke.

Was hoping someone from the group could offer some theories before I see a
diesel mechanic possibly tomorrow or weekend. Other possibilities I thought
were valve or tappets as these are usually at the top of the engine however
I am not mechanical at all so am guessing.