1 files changed, 77 insertions, 21 deletions

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index caa011008cd0..fc24eb9b3948 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -452,29 +452,85 @@ static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
         /* Grant backend access to each skb fragment page. */
         for (i = 0; i < frags; i++) {
                 skb_frag_t *frag = skb_shinfo(skb)->frags + i;
+                struct page *page = skb_frag_page(frag);
 
-                tx->flags |= XEN_NETTXF_more_data;
+                len = skb_frag_size(frag);
+                offset = frag->page_offset;
 
-                id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);
-                np->tx_skbs[id].skb = skb_get(skb);
-                tx = RING_GET_REQUEST(&np->tx, prod++);
-                tx->id = id;
-                ref = gnttab_claim_grant_reference(&np->gref_tx_head);
-                BUG_ON((signed short)ref < 0);
+                /* Data must not cross a page boundary. */
+                BUG_ON(len + offset > PAGE_SIZE<<compound_order(page));
 
-                mfn = pfn_to_mfn(page_to_pfn(skb_frag_page(frag)));
-                gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
-                                                mfn, GNTMAP_readonly);
+                /* Skip unused frames from start of page */
+                page += offset >> PAGE_SHIFT;
+                offset &= ~PAGE_MASK;
 
-                tx->gref = np->grant_tx_ref[id] = ref;
-                tx->offset = frag->page_offset;
-                tx->size = skb_frag_size(frag);
-                tx->flags = 0;
+                while (len > 0) {
+                        unsigned long bytes;
+
+                        BUG_ON(offset >= PAGE_SIZE);
+
+                        bytes = PAGE_SIZE - offset;
+                        if (bytes > len)
+                                bytes = len;
+
+                        tx->flags |= XEN_NETTXF_more_data;
+
+                        id = get_id_from_freelist(&np->tx_skb_freelist,
+                                                  np->tx_skbs);
+                        np->tx_skbs[id].skb = skb_get(skb);
+                        tx = RING_GET_REQUEST(&np->tx, prod++);
+                        tx->id = id;
+                        ref = gnttab_claim_grant_reference(&np->gref_tx_head);
+                        BUG_ON((signed short)ref < 0);
+
+                        mfn = pfn_to_mfn(page_to_pfn(page));
+                        gnttab_grant_foreign_access_ref(ref,
+                                                        np->xbdev->otherend_id,
+                                                        mfn, GNTMAP_readonly);
+
+                        tx->gref = np->grant_tx_ref[id] = ref;
+                        tx->offset = offset;
+                        tx->size = bytes;
+                        tx->flags = 0;
+
+                        offset += bytes;
+                        len -= bytes;
+
+                        /* Next frame */
+                        if (offset == PAGE_SIZE && len) {
+                                BUG_ON(!PageCompound(page));
+                                page++;
+                                offset = 0;
+                        }
+                }
         }
 
         np->tx.req_prod_pvt = prod;
 }
 
+/*
+ * Count how many ring slots are required to send the frags of this
+ * skb. Each frag might be a compound page.
+ */
+static int xennet_count_skb_frag_slots(struct sk_buff *skb)
+{
+        int i, frags = skb_shinfo(skb)->nr_frags;
+        int pages = 0;
+
+        for (i = 0; i < frags; i++) {
+                skb_frag_t *frag = skb_shinfo(skb)->frags + i;
+                unsigned long size = skb_frag_size(frag);
+                unsigned long offset = frag->page_offset;
+
+                /* Skip unused frames from start of page */
+                offset &= ~PAGE_MASK;
+
+                pages += PFN_UP(offset + size);
+        }
+
+        return pages;
+}
+
 static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         unsigned short id;
@@ -487,23 +543,23 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
         grant_ref_t ref;
         unsigned long mfn;
         int notify;
-        int frags = skb_shinfo(skb)->nr_frags;
+        int slots;
         unsigned int offset = offset_in_page(data);
         unsigned int len = skb_headlen(skb);
         unsigned long flags;
 
-        frags += DIV_ROUND_UP(offset + len, PAGE_SIZE);
-        if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
-                printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",
-                       frags);
-                dump_stack();
+        slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
+                xennet_count_skb_frag_slots(skb);
+        if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
+                net_alert_ratelimited(
+                        "xennet: skb rides the rocket: %d slots\n", slots);
                 goto drop;
         }
 
         spin_lock_irqsave(&np->tx_lock, flags);
 
         if (unlikely(!netif_carrier_ok(dev) ||
-                     (frags > 1 && !xennet_can_sg(dev)) ||
+                     (slots > 1 && !xennet_can_sg(dev)) ||
                      netif_needs_gso(skb, netif_skb_features(skb)))) {
                 spin_unlock_irqrestore(&np->tx_lock, flags);
                 goto drop;