From top of my head im sure after 2 years of smoking the effects are reversible, however after 10 years of smoking the effects are most of the time irreversible 
hope this helps!
Suggestion:
If you quit I would say almost all of the damage will be undone, a tiny fraction will never be undone, and you'll have some black spots on the lung.
Most likely if you quit now and avoid second-hand smoke, in 20 years you will be far better off than even a non-smoker who lives with a smoker.
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