No ships that I know of, other than Regent Seven Seas, allow smoking in any of the dining venues.
Carnival now has a couple of totally smoke free lounges on all of their ships, you'd just have to find out which have that designation.
RCI's Radiance of the Seas had the most restrictive smoking policy I've yet encountered (though I hadn't experienced the same on previous RCI cruises). On that ship, aside from the casino only 2 of the lounges had a smoking section, the rest were designated totally non smoking.