On 21.10.21 08:51, Christoph Hellwig wrote: > 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. Thanks, I can understand that. And IMHO that would be even possible with split types; the function prototype will simply have to look a little more fancy instead of replacing "struct page" by "struct folio". :) -- Thanks, David / dhildenb
