Technically, JACK has the correct answer.
Realistically, here's the issue. The reason why all these holes appeared is that I didn't spray enough water at a high pressure onto the ceiling in one go. The bond between the popcorn and the ceiling was too strong for me to use a knife to separate them. To make it worse, I subsequently sprayed more water with low pressure (little by little) and try to scratch. So you see some of the ceiling is totally wet and some lost the drywall paper.
What I should've done is to use a 1 gal. pump sprayer (cost $10 in HD/L) to spray pressured water onto the ceiling and then scratch.
After learning my mistake, the rest of the ceiling got scraped off very smoothly.