Rental property to personal use back to rental use

Hi, I rented our primary residence out from 2015 - June 2017 while overseas.  Moved back in as primary residence in June 2017.  Then, in July 2021 moved out and rented it back out.  Thus, how do I handle the back and forth in 2021 taxes?

Based on a previous discussion - my understanding is that I start this latest rental period as a new period/asset with the caveat that I have to adjust my cost basis down to account for the previous depreciation claimed in 2015-2017.  

So, in 2021 tax return I should do [building purchase] - [previous years depreciation] = [starting cost basis for new rental period] and start the 27.5 years over.

Is this correct?