Re: [PATCH v2 10/12] [xen] fix "direction" argument of iov_iter_kvec()

John Stoffel
2022-10-28T12:48:27Z

On Fri, Oct 28, 2022 at 03:33:50AM +0100, Al Viro wrote:
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
> drivers/xen/pvcalls-back.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> index d6f945fd4147..21b9c850a382 100644
> --- a/drivers/xen/pvcalls-back.c
> +++ b/drivers/xen/pvcalls-back.c
> @@ -129,13 +129,13 @@ static bool pvcalls_conn_back_read(void *opaque)
> if (masked_prod < masked_cons) {
> vec[0].iov_base = data->in + masked_prod;
> vec[0].iov_len = wanted;
> - iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, wanted);
> + iov_iter_kvec(&msg.msg_iter, READ, vec, 1, wanted);

Wouldn't it make more sense to use READER and WRITER here, since the
current READ/WRITE are 100% non-obvious? This is probably a bigger
change, but this just looks wrong and will be so easy for people to
screw up again and again down the line.

> } else {
> vec[0].iov_base = data->in + masked_prod;
> vec[0].iov_len = array_size - masked_prod;
> vec[1].iov_base = data->in;
> vec[1].iov_len = wanted - vec[0].iov_len;
> - iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, wanted);
> + iov_iter_kvec(&msg.msg_iter, READ, vec, 2, wanted);
> }
>
> atomic_set(&map->read, 0);
> @@ -188,13 +188,13 @@ static bool pvcalls_conn_back_write(struct sock_mapping *map)
> if (pvcalls_mask(prod, array_size) > pvcalls_mask(cons, array_size)) {
> vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
> vec[0].iov_len = size;
> - iov_iter_kvec(&msg.msg_iter, READ, vec, 1, size);
> + iov_iter_kvec(&msg.msg_iter, WRITE, vec, 1, size);
> } else {
> vec[0].iov_base = data->out + pvcalls_mask(cons, array_size);
> vec[0].iov_len = array_size - pvcalls_mask(cons, array_size);
> vec[1].iov_base = data->out;
> vec[1].iov_len = size - vec[0].iov_len;
> - iov_iter_kvec(&msg.msg_iter, READ, vec, 2, size);
> + iov_iter_kvec(&msg.msg_iter, WRITE, vec, 2, size);
> }
>
> atomic_set(&map->write, 0);
> --
> 2.30.2
>

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