There are a lot of websites based on CloudFlare is cannot be visited suddenly in China mainland today. I think it is not the GFW’s policy but CloudFlare itself.
The detail information of this problem is:
When a visitor visits any websites on CloudFlare (especially CloudFlare.com), the DNS results are CloudFlare’s cooperation edge nodes’ IP addresses in China mainland.
We all know a domain needs ICP certificated when it is being as a website (or use HTTP and HTTPS ports).
So CloudFlare should check its DNS policy ASAP.