[Xen-changelog] [xen-unstable] netfront: use skb.cb for storing private data

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1176812482 -3600
# Node ID 9cf4c575b50935e4c4fd3e42dfa8c7a468bf29fb
# Parent  7b391c27f410d429028ce56db0b37824020821e3
netfront: use skb.cb for storing private data

Netfront's use of nh.raw and h.raw for storing page+offset is a bit
hinky, and it breaks with upcoming network stack updates which reduce
these fields to sub-pointer sizes.  Fortunately, skb offers the "cb"
field specifically for stashing this kind of info, so use it.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
---
 linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff -r 7b391c27f410 -r 9cf4c575b509 
linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Tue Apr 17 
12:21:33 2007 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/netfront/netfront.c      Tue Apr 17 
13:21:22 2007 +0100
@@ -67,6 +67,13 @@
 #include <xen/platform-compat.h>
 #endif
 
+struct netfront_cb {
+       struct page *page;
+       unsigned offset;
+};
+
+#define NETFRONT_SKB_CB(skb)   ((struct netfront_cb *)((skb)->cb))
+
 /*
  * Mutually-exclusive module options to select receive data path:
  *  rx_copy : Packets are copied by network backend into local memory
@@ -1354,8 +1361,8 @@ err:
                        }
                }
 
-               skb->nh.raw = (void *)skb_shinfo(skb)->frags[0].page;
-               skb->h.raw = skb->nh.raw + rx->offset;
+               NETFRONT_SKB_CB(skb)->page = skb_shinfo(skb)->frags[0].page;
+               NETFRONT_SKB_CB(skb)->offset = rx->offset;
 
                len = rx->status;
                if (len > RX_COPY_THRESHOLD)
@@ -1439,11 +1446,11 @@ err:
                kfree_skb(skb);
 
        while ((skb = __skb_dequeue(&rxq)) != NULL) {
-               struct page *page = (struct page *)skb->nh.raw;
+               struct page *page = NETFRONT_SKB_CB(skb)->page;
                void *vaddr = page_address(page);
-
-               memcpy(skb->data, vaddr + (skb->h.raw - skb->nh.raw),
-                      skb_headlen(skb));
+               unsigned offset = NETFRONT_SKB_CB(skb)->offset;
+
+               memcpy(skb->data, vaddr + offset, skb_headlen(skb));
 
                if (page != skb_shinfo(skb)->frags[0].page)
                        __free_page(page);

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