Re: [PATCH v2 4/7] iov_iter: new iov_iter_pin_pages*() routines

Al Viro
2022-09-01T00:43:02Z

On Tue, Aug 30, 2022 at 09:18:40PM -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(), for user_backed_iter(i) and iov_iter_bvec(i)
> cases.
>
> 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().

What of ITER_PIPE (splice from O_DIRECT fd to a to pipe, for filesystem
that uses generic_file_splice_read())?