[Xen-devel] [PATCH 2/3] xen-netfront: refactor skb slot counting

[David Vrabel <david.vrabel@xxxxxxxxxx>]

A function to count the number of slots an skb needs is more useful
than one that counts the slots needed for only the frags.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 drivers/net/xen-netfront.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 22bcb4e..6b29b3a 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -521,13 +521,15 @@ static void xennet_make_frags(struct sk_buff *skb, struct 
netfront_queue *queue,
 }
 
 /*
- * Count how many ring slots are required to send the frags of this
- * skb. Each frag might be a compound page.
+ * Count how many ring slots are required to send this skb. Each frag
+ * might be a compound page.
  */
-static int xennet_count_skb_frag_slots(struct sk_buff *skb)
+static int xennet_count_skb_slots(struct sk_buff *skb)
 {
        int i, frags = skb_shinfo(skb)->nr_frags;
-       int pages = 0;
+       int pages;
+
+       pages = PFN_UP(offset_in_page(skb->data) + skb_headlen(skb));
 
        for (i = 0; i < frags; i++) {
                skb_frag_t *frag = skb_shinfo(skb)->frags + i;
@@ -597,8 +599,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct 
net_device *dev)
                goto drop;
        }
 
-       slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
-               xennet_count_skb_frag_slots(skb);
+       slots = xennet_count_skb_slots(skb);
        if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
                net_dbg_ratelimited("xennet: skb rides the rocket: %d slots, %d 
bytes\n",
                                    slots, skb->len);
-- 
1.7.10.4


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