[Devel] [PATCH vz9] fs/fuse kio: use iov_iter_get_pages2() + iov_iter_revert() scheme in do_recv_one_seg()

[Alexey Kuznetsov]

Ack.

Oh, we should rewrite this. It is not good as it is. To
tcp_read_sock() for tcp, I think
and whatever for unix.

On Fri, Mar 8, 2024 at 12:05 AM Konstantin Khorenko
<khorenko at virtuozzo.com> wrote:
>
> Mainstream has deprecated iov_iter_get_pages() + iov_iter_advance()
> scheme in favour of iov_iter_get_pages2() + iov_iter_revert(), so we
> have to use the new scheme as well.
>
> Fixes: 75259bc81b21 ("fs/fuse kio: remove iov_iter_for_each_range()
> usage")
>
> The problem has appeared on rebasing to RHEL9.4 BETA 5.14.0-425.el9
> kernel:
> https://virtuozzo.atlassian.net/browse/PSBM-154941
>
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
> ---
>  fs/fuse/kio/pcs/pcs_sock_io.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/kio/pcs/pcs_sock_io.c b/fs/fuse/kio/pcs/pcs_sock_io.c
> index 46de1023c876..189cf5c98c7d 100644
> --- a/fs/fuse/kio/pcs/pcs_sock_io.c
> +++ b/fs/fuse/kio/pcs/pcs_sock_io.c
> @@ -226,10 +226,15 @@ static int do_recv_one_seg(struct socket *sock, struct iov_iter *it, size_t left
>                 ssize_t len;
>                 struct page* page;
>
> -               len = iov_iter_get_pages(it, &page, size, 1, &offset);
> +               len = iov_iter_get_pages2(it, &page, size, 1, &offset);
>                 BUG_ON(len <=0);
>
>                 ret = do_sock_recv(sock, kmap(page) + offset, len);
> +               if (ret <= 0)
> +                       iov_iter_revert(it, len);
> +               else if (ret < len)
> +                       iov_iter_revert(it, len - ret);
> +
>                 kunmap(page);
>                 put_page(page);
>         }
> @@ -313,7 +318,6 @@ static void pcs_sockio_recv(struct pcs_sockio *sio)
>                                 n = do_recv_one_seg(sio->socket, it, (size_t)(msg_size - sio->read_offset));
>                                 if (n > 0) {
>                                         sio->read_offset += n;
> -                                       iov_iter_advance(it, n);
>                                 } else {
>                                         if (n == -EAGAIN || n == 0)
>                                                 return;
> --
> 2.39.3
>