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    SubjectRe: [RFC PATCH v4 02/17] vhost/vsock: read data from non-linear skb
    On Sat, Jun 03, 2023 at 11:49:24PM +0300, Arseniy Krasnov wrote:
    > This adds copying to guest's virtio buffers from non-linear skbs. Such
    > skbs are created by protocol layer when MSG_ZEROCOPY flags is used. It
    > changes call of 'copy_to_iter()' to 'skb_copy_datagram_iter()'. Second
    > function can read data from non-linear skb.
    >
    > See commit to 'net/vmw_vsock/virtio_transport_common.c' with the same
    > name for more details.
    >
    > Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
    > ---
    > drivers/vhost/vsock.c | 12 +++++++-----
    > 1 file changed, 7 insertions(+), 5 deletions(-)
    >
    > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
    > index 6578db78f0ae..b254aa4b756a 100644
    > --- a/drivers/vhost/vsock.c
    > +++ b/drivers/vhost/vsock.c
    > @@ -156,7 +156,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
    > }
    >
    > iov_iter_init(&iov_iter, ITER_DEST, &vq->iov[out], in, iov_len);
    > - payload_len = skb->len;
    > + payload_len = skb->len - VIRTIO_VSOCK_SKB_CB(skb)->frag_off;
    > hdr = virtio_vsock_hdr(skb);
    >
    > /* If the packet is greater than the space available in the
    > @@ -197,8 +197,10 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
    > break;
    > }
    >
    > - nbytes = copy_to_iter(skb->data, payload_len, &iov_iter);
    > - if (nbytes != payload_len) {
    > + if (skb_copy_datagram_iter(skb,
    > + VIRTIO_VSOCK_SKB_CB(skb)->frag_off,
    > + &iov_iter,
    > + payload_len)) {
    > kfree_skb(skb);
    > vq_err(vq, "Faulted on copying pkt buf\n");
    > break;
    > @@ -212,13 +214,13 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
    > vhost_add_used(vq, head, sizeof(*hdr) + payload_len);
    > added = true;
    >
    > - skb_pull(skb, payload_len);
    > + VIRTIO_VSOCK_SKB_CB(skb)->frag_off += payload_len;
    > total_len += payload_len;
    >
    > /* If we didn't send all the payload we can requeue the packet
    > * to send it with the next available buffer.
    > */
    > - if (skb->len > 0) {
    > + if (VIRTIO_VSOCK_SKB_CB(skb)->frag_off < skb->len) {
    > hdr->flags |= cpu_to_le32(flags_to_restore);
    >
    > /* We are queueing the same skb to handle
    > --
    > 2.25.1
    >

    LGTM.

    Reviewed-by: Bobby Eshleman <bobby.eshleman@bytedance.com>

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