process and requirements for extension of visa here in chengdu china???

You need to submit your application 7 days prior to the expiry of the duration specified in their S2, and provide following documents:
1. Valid Temporary Accommodation Registration Form issued by a local police station or a hotel.
2. Your residence permit.
3. Proof of family relationship or kinship, a marriage certificate, a birth certificate.
4. Application form with photo.
The processing takes about 5 working days.