vsock/virtio: support to send non-linear skb

[linux-2.6-block.git] / net / vmw_vsock / virtio_transport.c

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index e95df847176b6df78066dbf1d2c1808385110a05..73d730156349199da4335d7f8c5e7e38ad19b685 100644 (file)
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -63,6 +63,17 @@ struct virtio_vsock {
 
        u32 guest_cid;
        bool seqpacket_allow;
+
+       /* These fields are used only in tx path in function
+        * 'virtio_transport_send_pkt_work()', so to save
+        * stack space in it, place both of them here. Each
+        * pointer from 'out_sgs' points to the corresponding
+        * element in 'out_bufs' - this is initialized in
+        * 'virtio_vsock_probe()'. Both fields are protected
+        * by 'tx_lock'. +1 is needed for packet header.
+        */
+       struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1];
+       struct scatterlist out_bufs[MAX_SKB_FRAGS + 1];
 };
 
 static u32 virtio_transport_get_local_cid(void)
@@ -100,8 +111,8 @@ virtio_transport_send_pkt_work(struct work_struct *work)
        vq = vsock->vqs[VSOCK_VQ_TX];
 
        for (;;) {
-               struct scatterlist hdr, buf, *sgs[2];
                int ret, in_sg = 0, out_sg = 0;
+               struct scatterlist **sgs;
                struct sk_buff *skb;
                bool reply;
 
@@ -111,12 +122,43 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 
                virtio_transport_deliver_tap_pkt(skb);
                reply = virtio_vsock_skb_reply(skb);
-
-               sg_init_one(&hdr, virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb)));
-               sgs[out_sg++] = &hdr;
-               if (skb->len > 0) {
-                       sg_init_one(&buf, skb->data, skb->len);
-                       sgs[out_sg++] = &buf;
+               sgs = vsock->out_sgs;
+               sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
+                           sizeof(*virtio_vsock_hdr(skb)));
+               out_sg++;
+
+               if (!skb_is_nonlinear(skb)) {
+                       if (skb->len > 0) {
+                               sg_init_one(sgs[out_sg], skb->data, skb->len);
+                               out_sg++;
+                       }
+               } else {
+                       struct skb_shared_info *si;
+                       int i;
+
+                       /* If skb is nonlinear, then its buffer must contain
+                        * only header and nothing more. Data is stored in
+                        * the fragged part.
+                        */
+                       WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
+
+                       si = skb_shinfo(skb);
+
+                       for (i = 0; i < si->nr_frags; i++) {
+                               skb_frag_t *skb_frag = &si->frags[i];
+                               void *va;
+
+                               /* We will use 'page_to_virt()' for the userspace page
+                                * here, because virtio or dma-mapping layers will call
+                                * 'virt_to_phys()' later to fill the buffer descriptor.
+                                * We don't touch memory at "virtual" address of this page.
+                                */
+                               va = page_to_virt(skb_frag->bv_page);
+                               sg_init_one(sgs[out_sg],
+                                           va + skb_frag->bv_offset,
+                                           skb_frag->bv_len);
+                               out_sg++;
+                       }
                }
 
                ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
@@ -621,6 +663,7 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 {
        struct virtio_vsock *vsock = NULL;
        int ret;
+       int i;
 
        ret = mutex_lock_interruptible(&the_virtio_vsock_mutex);
        if (ret)
@@ -663,6 +706,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
        if (ret < 0)
                goto out;
 
+       for (i = 0; i < ARRAY_SIZE(vsock->out_sgs); i++)
+               vsock->out_sgs[i] = &vsock->out_bufs[i];
+
        rcu_assign_pointer(the_virtio_vsock, vsock);
 
        mutex_unlock(&the_virtio_vsock_mutex);