There's nothing worse than getting ready to go camping or breaking out your summer gear only to find mold or mildew removal is in order. No matter how good a job I think I do every year when putting up the gear something seems to slip through the cracks and allow mold and or mildew to take up their icky pungent residence on my gear. That was true for years and something I just accepted as part of enjoying the outdoors until a few tips taught me how to remove mold and mildew easily as well as help prevent it from returning.
We will start by assuming you already have mold or mildew on your canvas gear and have to get rid of it as quickly and thoroughly as possible. First you have to dry it out. The best way to do this in the case of a tent is to re-assemble it and let the air and sun work on it. For everything else you can hang it on lines or a paved surface like a patio or driveway. If you lay something out be sure to rotate it every once in awhile. If you don't feel it has dried to your satisfaction before sundown put it away in a dry place and resume dying in the morning. This is almost never necessary but just in case it is better to be vigilant.
The most popular methods for removing mold and mildew are generally using normal household concoctions involving Pine-Sol, Lysol, or any number of diluted mixtures which do work fairly well. Even more common is the use of any number of overpriced solutions purchased anywhere from drugstores to hardware stores which also work but aren't too environmentally friendly and generally come with an even worse lingering odor than Pine-Sol or Lysol which is not what you want either. Any of those things will work, just don't plan on escaping the smell anytime soon.
What works really well with no need for additional ventilation and is extremely cost efficient is white vinegar. It sounds too simple to work but t is the best thing I've ever found. For a very heavy accumulation or stain use it undiluted. For a light stain mix it with equal parts water or any varying mixture depending on the strength of the stain. What works best is spraying it on starting at the top and allowing it to run down the entire surface. Let it set in for a few minutes then mist it one more time and begin wiping the surface down with a dry rag. This works not only on canvas, but tile, furniture, painted surfaces, plastic, or pretty much anything mold or mildew makes it's home, even wet clothes. It is color safe so you never have to worry about it fading anything. The real bonus, especially if you are going to be using it in th immediate future the smell dissipates quickly which is huge.
A little bonus tip when it comes to dealing with mold and mildew on canvas is to put white vinegar in a misting spray bottle and give all your canvas surfaces a light spray down before you put it away for the season. It's not 100% but it works far more often than it doesn't and can save you a headache the following year. Whatever you choose as your method of removal be thorough and if using anything along the lines of an industrial remover or household cleaner be sure to ventilate the area to avoid any potential complications.