How could a wood and fabric aircraft be controlled after a fabric tear mid-flight?
A wing tear is not something people train for because the impact on the airplane depends on where it is, how big it is, and what other systems have been damaged. If it's just a fabric tear then the damaged wing will produce less lift than the good one, meaning the airplane will want to roll in the direction of the damaged wing. For a pilot to survive there needs to be enough aileron and rudder authority to compensate for this and keep the plane level. So the first priority is to maintain positive control of the airplane and learn how to fly it again by using control inputs against the rolling action. If I feel like I need more aileron power I would decrease speed from cruise in small increments, seeing how a slower speed effects my ability to control the airplane, if it reduces the rolling and gives me better control then I'll keep decreasing speed bit by bit to find a sweet spot. If the damage happens at a slow speed, like in a climb, I would increase speed by increments. I would keep a very healthy margin above stall speed though, as the damage to the wing has probably increased the stall speed of the damaged wing. If the damaged wing stalls then I'm in a snap roll and unlikely to recover. 

Once I have control I want to land as soon as I can, and I ideally want a very long runway into wind with emergency services. If I know the area well I probably already know where I want to go. If I can't maintain altitude then I need to find a big field, quick. 

Once I've aviated an navigated I will communicate and declare an emergency with ATC and state my intentions. ATC can't help me fly the airplane so I didn't need them before now, but now they can help reduce my workload. If I don't know the area ATC can help me find the best place to go, and they can give me weather information and notify emergency services. 

Once I get to an airfield comes the tricky part - landing. It's tricky because I don't know when the damaged wing is going to stall, so I have to keep a lot of extra airspeed on approach and landing without flaps (flaps will change the shape of the wing and the dynamics of the situation in ways I cannot anticipate). This means a faster approach and putting the wheels on the ground at a much faster speed - this is why I would want a really long strip. Once the wheels are on the ground if one wing stalls before the other I can probably control it, and the wheels will help give some stability as well while I gently brake.