On Sat, Aug 27, 2022 at 01:36:04AM -0700, John Hubbard wrote:

Provide two new wrapper routines that are intended for user space pages
only:

    iov_iter_pin_pages()
    iov_iter_pin_pages_alloc()

Internally, these routines call pin_user_pages_fast(), instead of
get_user_pages_fast().

As always, callers must use unpin_user_pages() or a suitable FOLL_PIN
variant, to release the pages, if they actually were acquired via
pin_user_pages_fast().

This is a prerequisite to converting bio/block layers over to use
pin_user_pages_fast().

You do realize that O_DIRECT on ITER_BVEC is possible, right?