Where in Shanghai can you get a visa extension? What docs must be produced to obtain an extension?

You need to go to Exit-Entry Administrative Bureau of Shanghai Public Security Bureau to apply for visa extension.

Address: 1500 Mingsheng Road, Pudong New Area, Shanghai.
Office hours: 09:00-17:00, Monday-Saturday (except Chinese public holidays)
Enquiry Tel: 28951900

The required documents for visa extension:
1. your passport
2. the copy of visa page on your passport
3. accommodation registration sheet issued by a hotel in Shanghai or the police station where you reside.
4. the documents to prove the purpose of a longer stay duration.