Re: [RFC PATCH net-next 01/12] vhost_net: introduce helper to initialize tx iov iter

Jesse Brandeburg
2018-05-21T16:24:03Z

Hi Jason, a few nits.

On Mon, 21 May 2018 17:04:22 +0800 Jason wrote:
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/vhost/net.c | 34 +++++++++++++++++++++++-----------
> 1 file changed, 23 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index c4b49fc..15d191a 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -459,6 +459,26 @@ static bool vhost_exceeds_maxpend(struct vhost_net *net)
> min_t(unsigned int, VHOST_MAX_PEND, vq->num >> 2);
> }
>
> +static size_t init_iov_iter(struct vhost_virtqueue *vq, struct iov_iter *iter,
> + size_t hdr_size, int out)
> +{
> + /* Skip header. TODO: support TSO. */
> + size_t len = iov_length(vq->iov, out);
> +
> + iov_iter_init(iter, WRITE, vq->iov, out, len);
> + iov_iter_advance(iter, hdr_size);
> + /* Sanity check */
> + if (!iov_iter_count(iter)) {
> + vq_err(vq, "Unexpected header len for TX: "
> + "%zd expected %zd\n",
> + len, hdr_size);

ok, it was like this before, but please unwrap the string in " ", there
should be no line breaks in string declarations and they are allowed to
go over 80 characters.

> + return -EFAULT;
> + }
> + len = iov_iter_count(iter);
> +
> + return len;
> +}
> +
> /* Expects to be always run from workqueue - which acts as
> * read-size critical section for our kind of RCU. */
> static void handle_tx(struct vhost_net *net)
> @@ -521,18 +541,10 @@ static void handle_tx(struct vhost_net *net)
> "out %d, int %d\n", out, in);
> break;
> }
> - /* Skip header. TODO: support TSO. */
> - len = iov_length(vq->iov, out);
> - iov_iter_init(&msg.msg_iter, WRITE, vq->iov, out, len);
> - iov_iter_advance(&msg.msg_iter, hdr_size);
> - /* Sanity check */
> - if (!msg_data_left(&msg)) {
> - vq_err(vq, "Unexpected header len for TX: "
> - "%zd expected %zd\n",
> - len, hdr_size);
> +
> + len = init_iov_iter(vq, &msg.msg_iter, hdr_size, out);
> + if (len < 0)

len is declared as size_t, which is unsigned, and can never be
negative. I'm pretty sure this is a bug.

> break;
> - }
> - len = msg_data_left(&msg);
>
> zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
> && !vhost_exceeds_maxpend(net)