A few years ago something similar happened to me when I brought my 91 940 into Jiffy Lube (the last time I went there also).
Instead of 5, they put 7 quarts of oil in! When I left the shop a huge cloud of smoke came out of the tail pipe, and I brought it right back in. Looking at it (no one ever thought of checking the oil level) they thought some oil spilled on the exhaust pipe and smoked. They cleaned it up, I left, and it seemed better, but after a few miles it smoked again. I immediately pulled over and called a tow truck, who took it to a local mechanic friend of mine. He discovered the problem and drained the excess oil, and thought all was fine. I then took it to a Volvo shop who also checked it out, and found no problems.
Hopefully yours will be ok also.