Did we document all this? :) It'd be good to be super explicit about these sorts of 'dependency chains'.
Documentation/admin-guide/mm/transhuge.rst has under "Global THP controls" quite some stuff about all that, yes.
The whole document needs an overhaul, to clarify on the whole terminology, make it consistent, and better explain how the pagecache behaves etc. On my todo list, but I'm afraid it will be a bit of work to get it right / please most people.
-- Cheers, David / dhildenb
