On Sun, Aug 28, 2022 at 01:38:57AM +0100, Al Viro wrote: > On Sat, Aug 27, 2022 at 04:55:18PM -0700, John Hubbard wrote: > > On 8/27/22 15:48, Al Viro wrote: > > > On Sat, Aug 27, 2022 at 01:36:06AM -0700, John Hubbard wrote: > > >> Convert the NFS Direct IO layer to use pin_user_pages_fast() and > > >> unpin_user_page(), instead of get_user_pages_fast() and put_page(). > > > > > > Again, this stuff can be hit with ITER_BVEC iterators > > > > > >> - result = iov_iter_get_pages_alloc2(iter, &pagevec, > > >> + result = dio_w_iov_iter_pin_pages_alloc(iter, &pagevec, > > >> rsize, &pgbase); > > > > > > and this will break on those. > > > > If anyone has an example handy, of a user space program that leads > > to this situation (O_DIRECT with ITER_BVEC), it would really help > > me reach enlightenment a lot quicker in this area. :) > > Er... splice(2) to O_DIRECT-opened file on e.g. ext4? Or > sendfile(2) to the same, for that matter... s/ext4/nfs/ to hit this particular codepath, obviously.
