On Wed, Oct 20, 2021 at 08:04:56PM +0200, David Hildenbrand wrote: > real): assume we have to add a field for handling something about anon > THP in the struct page (let's assume in the head page for simplicity). > Where would we add it? To "struct folio" and expose it to all other > folios that don't really need it because it's so special? To "struct > page" where it actually doesn't belong after all the discussions? And if > we would have to move that field it into a tail page, it would get even > more "tricky". > > Of course, we could let all special types inherit from "struct folio", > which inherit from "struct page" ... but I am not convinced that we > actually want that. After all, we're C programmers ;) > > But enough with another side-discussion :) FYI, with my block and direct I/O developer hat on I really, really want to have the folio for both file and anon pages. Because to make the get_user_pages path a _lot_ more efficient it should store folios. And to make that work I need them to work for file and anon pages because for get_user_pages and related code they are treated exactly the same.
