xen/netback: add fraglist support for to-guest rx

This allows full 64K skbuffs (with 1500 mtu ethernet, composed of 45
fragments) to be handled by netback for to-guest rx.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
[re-based]
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 30 insertions, 10 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 211d542a830b..4af532a67d95 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -467,7 +467,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
         dev->netdev_ops = &xenvif_netdev_ops;
         dev->hw_features = NETIF_F_SG |
                 NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
-                NETIF_F_TSO | NETIF_F_TSO6;
+                NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_FRAGLIST;
         dev->features = dev->hw_features | NETIF_F_RXCSUM;
         dev->ethtool_ops = &xenvif_ethtool_ops;
 
diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
index 8c8c5b5883eb..8e9ade6ccf18 100644
--- a/drivers/net/xen-netback/rx.c
+++ b/drivers/net/xen-netback/rx.c
@@ -215,7 +215,8 @@ static unsigned int xenvif_gso_type(struct sk_buff *skb)
 struct xenvif_pkt_state {
         struct sk_buff *skb;
         size_t remaining_len;
-        int frag; /* frag == -1 => skb->head */
+        struct sk_buff *frag_iter;
+        int frag; /* frag == -1 => frag_iter->head */
         unsigned int frag_offset;
         struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
         unsigned int extra_count;
@@ -237,6 +238,7 @@ static void xenvif_rx_next_skb(struct xenvif_queue *queue,
         memset(pkt, 0, sizeof(struct xenvif_pkt_state));
 
         pkt->skb = skb;
+        pkt->frag_iter = skb;
         pkt->remaining_len = skb->len;
         pkt->frag = -1;
 
@@ -293,20 +295,40 @@ static void xenvif_rx_complete(struct xenvif_queue *queue,
         __skb_queue_tail(queue->rx_copy.completed, pkt->skb);
 }
 
+static void xenvif_rx_next_frag(struct xenvif_pkt_state *pkt)
+{
+        struct sk_buff *frag_iter = pkt->frag_iter;
+        unsigned int nr_frags = skb_shinfo(frag_iter)->nr_frags;
+
+        pkt->frag++;
+        pkt->frag_offset = 0;
+
+        if (pkt->frag >= nr_frags) {
+                if (frag_iter == pkt->skb)
+                        pkt->frag_iter = skb_shinfo(frag_iter)->frag_list;
+                else
+                        pkt->frag_iter = frag_iter->next;
+
+                pkt->frag = -1;
+        }
+}
+
 static void xenvif_rx_next_chunk(struct xenvif_queue *queue,
                                  struct xenvif_pkt_state *pkt,
                                  unsigned int offset, void **data,
                                  size_t *len)
 {
-        struct sk_buff *skb = pkt->skb;
+        struct sk_buff *frag_iter = pkt->frag_iter;
         void *frag_data;
         size_t frag_len, chunk_len;
 
+        BUG_ON(!frag_iter);
+
         if (pkt->frag == -1) {
-                frag_data = skb->data;
-                frag_len = skb_headlen(skb);
+                frag_data = frag_iter->data;
+                frag_len = skb_headlen(frag_iter);
         } else {
-                skb_frag_t *frag = &skb_shinfo(skb)->frags[pkt->frag];
+                skb_frag_t *frag = &skb_shinfo(frag_iter)->frags[pkt->frag];
 
                 frag_data = skb_frag_address(frag);
                 frag_len = skb_frag_size(frag);
@@ -322,10 +344,8 @@ static void xenvif_rx_next_chunk(struct xenvif_queue *queue,
         pkt->frag_offset += chunk_len;
 
         /* Advance to next frag? */
-        if (frag_len == chunk_len) {
-                pkt->frag++;
-                pkt->frag_offset = 0;
-        }
+        if (frag_len == chunk_len)
+                xenvif_rx_next_frag(pkt);
 
         *data = frag_data;
         *len = chunk_len;