On Thu, Sep 22, 2022 at 07:31:36AM -0700, Christoph Hellwig wrote: > On Wed, Sep 14, 2022 at 04:51:17AM +0100, Al Viro wrote: > > Unless I'm misreading Jan, the question is whether they should get or > > pin. > > And I think the answer is: inside ->read_iter or ->write_iter they > should neither get or pin. The callers of it need to pin the pages > if they are pagecache pages that can potentially be written to through > shared mappings, else a get would be enough. But the method instance > should not have to care and just be able to rely on the caller making > sure they do not go away. The interesting part, AFAICS, is where do we _unpin_ them and how do we keep track which pages (obtained from iov_iter_get_pages et.al.) need to be unpinned. > > I'm really tempted to slap > > if (WARN_ON(i->data_source)) > > return 0; > > into copy_to_iter() et.al., along with its opposite for copy_from_iter(). > > Ys, I think that would be useful. And we could use something more > descriptive than READ/WRITE to start with. See #work.iov_iter; done, but it took a bit of fixing the places that create iov_iter instances.
