Since your mortgage was acquired in 2016, your principal loan is grandfathered in and the interest is deductible for up to $1M in debt. For loans originating after Dec. 14, 2017, the interest is still deductible but limited to the interest on $750K of debt.
Beginning in 2018, the interest on the 'general purpose' debt is no longer deductible as it was in the past. Beginning in 2018, the interest on home equity debt is no longer deductible unless it was used to buy, build, or substantially improve your home. See this article for more details on the mortgage interest deduction and how it has changed. Deducting Mortgage Interest
