On Fri, Sep 15, 2023 at 07:54:50PM +0200, Claudio Imbrenda wrote: > On Fri, 15 Sep 2023 18:28:25 +0100 > "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> wrote: > > > We introduced arch_make_folio_accessible() a couple of years > > ago, and it's in use in the page writeback path. GUP still uses > > arch_make_page_accessible(), which means that we can succeed in making > > a single page of a folio accessible, then fail to make the rest of the > > folio accessible when it comes time to do writeback and it's too late > > to do anything about it. I'm not sure how much of a real problem this is. > > > > Switching everything around to arch_make_folio_accessible() also lets > > us switch the page flag to be per-folio instead of per-page, which is > > a good step towards dynamically allocated folios. > > if I understand correctly, this will as a matter of fact move the > security property from pages to folios. Correct. > this means that trying to access a page will (try to) make the whole > folio accessible, even though that might be counterproductive.... > > and there is no way to simply split a folio > > I don't like this As I said in the cover letter, we already make the entire folio accessible in the writeback path. I suppose if you never write the folio back, this is new ... Anyway, looking forward to a more substantial discussion on Monday.