Ben MacIntyre in the Times Online:
Some writers simply could not do one without the other. Sir Compton Mackenzie wrote 81 books by the age of 74, having smoked, according to his own estimate, at least half a ton of tobacco. 'The harder I work,' he declared, 'the more I need to smoke because tobacco is the handmaid of literature.'
A less likely apostle for smoking was J. M. Barrie who wrote My Lady Nicotine: A Study in Smoke, 14 years before the arrival of Peter Pan. Barrie taught generations of children to believe in fairies; he, on the other hand, believed in the magic of smoking. With the introduction of tobacco, England woke up from a long sleep, he wrote in 1896. 'Suddenly a new zest had been given to life.'
Mikhail Bakhtin may be the only writer who actually smoked what he wrote. Driven to distraction by a wartime shortage of cigarette papers, the Russian literary theorist ended up smoking the manuscript of his book on the Bildungsroman. Others found the joys of smoking superior to all other earthly temptations: 'A woman is only a woman,' Rudyard Kipling wrote in The Betrothed, 'but a good cigar is a smoke.'
Actually, though, I feel many writers over the years must have smoked what they have written when cigarette papers ran in short supply.
(Thanks to Sarah for the link.)