vhost: don't bother with copying iovec in handle_tx()

just advance the msg.msg_iter and be done with that.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 6906f76332f4a91020a45ef04b538ca62b0cf3fe..d86cc9bb9ea4e16060fbaa414934f3f97bf85f9d 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -336,7 +336,7 @@ static void handle_tx(struct vhost_net *net)
 {
        struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
        struct vhost_virtqueue *vq = &nvq->vq;
-       unsigned out, in, s;
+       unsigned out, in;
        int head;
        struct msghdr msg = {
                .msg_name = NULL,
@@ -395,16 +395,17 @@ static void handle_tx(struct vhost_net *net)
                        break;
                }
                /* Skip header. TODO: support TSO. */
-               s = move_iovec_hdr(vq->iov, nvq->hdr, hdr_size, out);
                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 (!len) {
+               if (!iov_iter_count(&msg.msg_iter)) {
                        vq_err(vq, "Unexpected header len for TX: "
                               "%zd expected %zd\n",
-                              iov_length(nvq->hdr, s), hdr_size);
+                              len, hdr_size);
                        break;
                }
+               len = iov_iter_count(&msg.msg_iter);
 
                zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
                                   && (nvq->upend_idx + 1) % UIO_MAXIOV !=