On Mon, Jul 29, 2019 at 04:57:21PM -0400, Jerome Glisse wrote: > > All pages releases by bio_release_pages should come from > > get_get_user_pages, so I don't really see the point here. > > No they do not all comes from GUP for see various callers > of bio_check_pages_dirty() for instance iomap_dio_zero() > > I have carefully tracked down all this and i did not do > anyconvertion just for the fun of it :) Well, the point is _should_ not necessarily do. iomap_dio_zero adds the ZERO_PAGE, which we by definition don't need to refcount. So we can mark this bio BIO_NO_PAGE_REF safely after removing the get_page there. Note that the equivalent in the old direct I/O code, dio_refill_pages, will be a little more complicated as it can match user pages and the ZERO_PAGE in a single bio, so a per-bio flag won't handle it easily. Maybe we just need to use a separate bio there as well. In general with series like this we should not encode the status quo an pile new hacks upon the old one, but thing where we should be and fix up the old warts while having to wade through all that code.
