On Thu, Nov 16, 2023 at 07:10:01PM +0800, Yunsheng Lin wrote: > On 2023/11/15 21:38, Jason Gunthorpe wrote: > > On Wed, Nov 15, 2023 at 05:21:02PM +0800, Yunsheng Lin wrote: > > > >>>>> I would expect net stack, page pool, driver still see the 'struct page', > >>>>> only memory provider see the specific struct for itself, for the above, > >>>>> devmem memory provider sees the 'struct page_pool_iov'. > >>>>> > >>>>> The reason I still expect driver to see the 'struct page' is that driver > >>>>> will still need to support normal memory besides devmem. > >>> > >>> I wouldn't say this approach is unreasonable, but it does have to be > >>> done carefully to isolate the mm. Keeping the struct page in the API > >>> is going to make this very hard. > >> > >> I would expect that most of the isolation is done in page pool, as far as > >> I can see: > > > > It is the sort of thing that is important enough it should have > > compiler help via types to prove that it is being done > > properly. Otherwise it will be full of mistakes over time. > > Yes, agreed. > > I have done something similar as willy has done for some of > folio conversion as below: That is not at all what I mean, I mean you should not use struct page * types at all in code that flows from the _iov version except via limited accessors that can be audited and have appropriate assertions. Just releasing struct page * that is not a struct page * everywhere without type safety will never be correct long term. Jason
