Don't fight it in the small passage. Fight where you can move. Use a fire or a bow and run circles around it. Use boulders as cover. The troll will have to move around them. That should give you enough time to run, shoot and heal.
A sword and shield follower (you will have Lydia by then) can be handy to act as a tank if your a ranged character. If your going up the mountain at a very low level keep on your toes though as the Troll can easily overwelm the follower and you'll have to use 87.152's kiting method until the follower recovers.
If you really want to be a jerk lure the Troll to the pilgrims you find on the mountain (or all the way down to Ivarstead) Frost Trolls are nasty though they might not last long.
Frost Trolls have a weakness to fire so fire based spells and fire enchanted weapons are suggested. They also have very fast health regeneration so poisons can halt that temporarily. Ranged attacks are suggested but if you can't, try dodging the slow attacks by walking back and forth when it strikes. At lower levels a melee oriented follower with a shield or heavy armor is suggested. If all else fails, run. You run and walk faster than a Frost Troll at full speed.
i kited him to the edge of the mountain path and through a intricate dance of "fus" and power attacks he eventually inched himself off the side. The fall didn't quite kill him but I was able to finish him off with an arrow before his health regenerated.
I heard if you read the Tablet Etchings along the path of The Seven Thousand Steps you'll recieve the blessing Voice of the Sky which makes all animals friendly to the dragonborn... Do trolls count as animals? I bet that would be handy when you are descending the 7000 steps. :D
Yeah I usually run past it now on high levels (to lazy to fight) or take a follower along to distract it while I kill it from safe distance if all else fails pick up ash shell spell in the dragonborn dlc (or a paralysis spell if you can) use that unless youre on high difficulty using starting gear and spells you won't really have nay problem with it anyway, I never have.
I avoided the troll many times but am currently on a mage playthrough (playing the entire game, every main side guild DLC quest apart from misc quests like bounty getting and collecting and delivering stuff) and some fire kills it off pretty quickly.
But I avoided the Main Questline until Level 11 as I was focusing on the College Questline so I have better destruction so it's probably different for me.