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...
