[PATCH 6/9] virtio-net: unmark scatterlist ending after virtqueue_add_buf
From: Paolo Bonzini <pbonzini@redhat.com>
Date: 2013-02-12 12:25:12
Also in:
kvm, lkml
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
Prepare for when virtqueue_add_buf will use sg_next instead of ignoring ending markers. Note that for_each_sg (and thus virtqueue_add_sg) allows you to pass a "truncated" scatterlist that does not have a marker on the last item. We rely on this in add_recvbuf_mergeable. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- drivers/net/virtio_net.c | 19 ++++++++++++++----- 1 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 35c00c5..78b6f51 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -440,13 +440,16 @@ static int add_recvbuf_small(struct receive_queue *rq, gfp_t gfp) hdr = skb_vnet_hdr(skb); sg_set_buf(rq->sg, &hdr->hdr, sizeof hdr->hdr); - skb_to_sgvec(skb, rq->sg + 1, 0, skb->len); err = virtqueue_add_buf(rq->vq, rq->sg, 0, 2, skb, gfp); if (err < 0) dev_kfree_skb(skb); + /* An optimization: clear the end bit set by skb_to_sgvec, so + * we can simply re-use rq->sg[] next time. + */ + sg_unmark_end(rq->sg + 1); return err; }
@@ -505,8 +508,7 @@ static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp) if (!page) return -ENOMEM; - sg_init_one(rq->sg, page_address(page), PAGE_SIZE); - + sg_set_page(rq->sg, page, PAGE_SIZE, 0); err = virtqueue_add_buf(rq->vq, rq->sg, 0, 1, page, gfp); if (err < 0) give_pages(rq, page);
@@ -671,6 +673,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest; struct virtnet_info *vi = sq->vq->vdev->priv; unsigned num_sg; + int ret; pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
@@ -710,8 +713,14 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) sg_set_buf(sq->sg, &hdr->hdr, sizeof hdr->hdr); num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1; - return virtqueue_add_buf(sq->vq, sq->sg, num_sg, - 0, skb, GFP_ATOMIC); + ret = virtqueue_add_buf(sq->vq, sq->sg, num_sg, + 0, skb, GFP_ATOMIC); + + /* An optimization: clear the end bit set by skb_to_sgvec, so + * we can simply re-use sq->sg[] next time. + */ + sg_unmark_end(&sq->sg[num_sg-1]); + return ret; } static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
--
1.7.1