[RFC][PATCH v6 09/19] Ignore room skb_reserve() when device is using external buffer.

From: xiaohui . xin
Date: Fri May 21 2010 - 05:27:21 EST

From: Xin Xiaohui <xiaohui.xin@xxxxxxxxx>

Make the skb->data and skb->head from external buffer
to be consistent, we ignore the room reserved by driver
for kernel skb.

Signed-off-by: Xin Xiaohui <xiaohui.xin@xxxxxxxxx>
Signed-off-by: Zhao Yu <yzhao81new@xxxxxxxxx>
Reviewed-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
include/linux/skbuff.h | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5ff8c27..193b259 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1200,6 +1200,15 @@ static inline int skb_tailroom(const struct sk_buff *skb)
static inline void skb_reserve(struct sk_buff *skb, int len)
+ /* Since skb_reserve() is only for an empty buffer,
+ * and when the skb is getting external buffer, we cannot
+ * retain the external buffer has the same reserved space
+ * in the header which kernel allocatd skb has, so have to
+ * ignore this. And we have recorded the external buffer
+ * info in the destructor_arg field, so use it as indicator.
+ */
+ if (skb_shinfo(skb)->destructor_arg)
+ return;
skb->data += len;
skb->tail += len;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/