virtio-net: move sg off stack

Move sg structure off stack and into virtnet_info structure.
This helps remove extra sg_init_table calls as well as reduce
stack usage.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ecec9a8527f357bdafcc7fe9ff4c180ace3510fd..b81e452d4ba2b7914d9f09e2dbfc084a71e7bb45 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -39,8 +39,7 @@ module_param(gso, bool, 0444);
 
 #define VIRTNET_SEND_COMMAND_SG_MAX    2
 
-struct virtnet_info
-{
+struct virtnet_info {
        struct virtio_device *vdev;
        struct virtqueue *rvq, *svq, *cvq;
        struct net_device *dev;
@@ -61,6 +60,10 @@ struct virtnet_info
 
        /* Chain pages by the private ptr. */
        struct page *pages;
+
+       /* fragments + linear part + virtio header */
+       struct scatterlist rx_sg[MAX_SKB_FRAGS + 2];
+       struct scatterlist tx_sg[MAX_SKB_FRAGS + 2];
 };
 
 struct skb_vnet_hdr {
@@ -323,10 +326,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
 {
        struct sk_buff *skb;
        struct skb_vnet_hdr *hdr;
-       struct scatterlist sg[2];
        int err;
 
-       sg_init_table(sg, 2);
        skb = netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN);
        if (unlikely(!skb))
                return -ENOMEM;
@@ -334,11 +335,11 @@ static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
        skb_put(skb, MAX_PACKET_LEN);
 
        hdr = skb_vnet_hdr(skb);
-       sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr);
+       sg_set_buf(vi->rx_sg, &hdr->hdr, sizeof hdr->hdr);
 
-       skb_to_sgvec(skb, sg + 1, 0, skb->len);
+       skb_to_sgvec(skb, vi->rx_sg + 1, 0, skb->len);
 
-       err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 2, skb);
+       err = vi->rvq->vq_ops->add_buf(vi->rvq, vi->rx_sg, 0, 2, skb);
        if (err < 0)
                dev_kfree_skb(skb);
 
@@ -347,13 +348,11 @@ static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
 
 static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
 {
-       struct scatterlist sg[MAX_SKB_FRAGS + 2];
        struct page *first, *list = NULL;
        char *p;
        int i, err, offset;
 
-       sg_init_table(sg, MAX_SKB_FRAGS + 2);
-       /* page in sg[MAX_SKB_FRAGS + 1] is list tail */
+       /* page in vi->rx_sg[MAX_SKB_FRAGS + 1] is list tail */
        for (i = MAX_SKB_FRAGS + 1; i > 1; --i) {
                first = get_a_page(vi, gfp);
                if (!first) {
@@ -361,7 +360,7 @@ static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
                                give_pages(vi, list);
                        return -ENOMEM;
                }
-               sg_set_buf(&sg[i], page_address(first), PAGE_SIZE);
+               sg_set_buf(&vi->rx_sg[i], page_address(first), PAGE_SIZE);
 
                /* chain new page in list head to match sg */
                first->private = (unsigned long)list;
@@ -375,17 +374,17 @@ static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
        }
        p = page_address(first);
 
-       /* sg[0], sg[1] share the same page */
-       /* a separated sg[0] for  virtio_net_hdr only during to QEMU bug*/
-       sg_set_buf(&sg[0], p, sizeof(struct virtio_net_hdr));
+       /* vi->rx_sg[0], vi->rx_sg[1] share the same page */
+       /* a separated vi->rx_sg[0] for virtio_net_hdr only due to QEMU bug */
+       sg_set_buf(&vi->rx_sg[0], p, sizeof(struct virtio_net_hdr));
 
-       /* sg[1] for data packet, from offset */
+       /* vi->rx_sg[1] for data packet, from offset */
        offset = sizeof(struct padded_vnet_hdr);
-       sg_set_buf(&sg[1], p + offset, PAGE_SIZE - offset);
+       sg_set_buf(&vi->rx_sg[1], p + offset, PAGE_SIZE - offset);
 
        /* chain first in list head */
        first->private = (unsigned long)list;
-       err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, MAX_SKB_FRAGS + 2,
+       err = vi->rvq->vq_ops->add_buf(vi->rvq, vi->rx_sg, 0, MAX_SKB_FRAGS + 2,
                                       first);
        if (err < 0)
                give_pages(vi, first);
@@ -396,16 +395,15 @@ static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
 static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
 {
        struct page *page;
-       struct scatterlist sg;
        int err;
 
        page = get_a_page(vi, gfp);
        if (!page)
                return -ENOMEM;
 
-       sg_init_one(&sg, page_address(page), PAGE_SIZE);
+       sg_init_one(vi->rx_sg, page_address(page), PAGE_SIZE);
 
-       err = vi->rvq->vq_ops->add_buf(vi->rvq, &sg, 0, 1, page);
+       err = vi->rvq->vq_ops->add_buf(vi->rvq, vi->rx_sg, 0, 1, page);
        if (err < 0)
                give_pages(vi, page);
 
@@ -514,12 +512,9 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
 
 static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
-       struct scatterlist sg[2+MAX_SKB_FRAGS];
        struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
        const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 
-       sg_init_table(sg, 2+MAX_SKB_FRAGS);
-
        pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
 
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
@@ -553,12 +548,13 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 
        /* Encode metadata header at front. */
        if (vi->mergeable_rx_bufs)
-               sg_set_buf(sg, &hdr->mhdr, sizeof hdr->mhdr);
+               sg_set_buf(vi->tx_sg, &hdr->mhdr, sizeof hdr->mhdr);
        else
-               sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr);
+               sg_set_buf(vi->tx_sg, &hdr->hdr, sizeof hdr->hdr);
 
-       hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
-       return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb);
+       hdr->num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
+       return vi->svq->vq_ops->add_buf(vi->svq, vi->tx_sg, hdr->num_sg,
+                                       0, skb);
 }
 
 static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
@@ -940,6 +936,8 @@ static int virtnet_probe(struct virtio_device *vdev)
        vdev->priv = vi;
        vi->pages = NULL;
        INIT_DELAYED_WORK(&vi->refill, refill_work);
+       sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
+       sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
 
        /* If we can receive ANY GSO packets, we must allocate large ones. */
        if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||