144 hour in shanghai ??

Hi - We would like to fly from Minneapolis (US) to Canada (4hour layover) to Shanghai. Spend 6 days in Shanghai and then return fly back to Canada (2 hour layover) and back to minneapolis (US). Is this acceptable for the 144 hours in Shanghai VISA FREE? Do we need to spend the night in Canada on the way home? Or do I need to stop in Japan or Hawaii for a night or 2?