[NET]: Uninline kfree_skb and allow NULL argument

o Uninline kfree_skb, which saves some 15k of object code on my notebook.

o Allow kfree_skb to be called with a NULL argument.

  Subsequent patches can remove conditional from drivers and further
  reduce source and object size.

Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -304,6 +304,7 @@ struct sk_buff {
 
 #include <asm/system.h>
 
+extern void kfree_skb(struct sk_buff *skb);
 extern void	       __kfree_skb(struct sk_buff *skb);
 extern struct sk_buff *__alloc_skb(unsigned int size,
 				   gfp_t priority, int fclone);
@@ -403,22 +404,6 @@ static inline struct sk_buff *skb_get(struct sk_buff *skb)
  * atomic change.
  */
 
-/**
- *	kfree_skb - free an sk_buff
- *	@skb: buffer to free
- *
- *	Drop a reference to the buffer and free it if the usage count has
- *	hit zero.
- */
-static inline void kfree_skb(struct sk_buff *skb)
-{
-	if (likely(atomic_read(&skb->users) == 1))
-		smp_rmb();
-	else if (likely(!atomic_dec_and_test(&skb->users)))
-		return;
-	__kfree_skb(skb);
-}
-
 /**
  *	skb_cloned - is the buffer a clone
  *	@skb: buffer to check

net/core/skbuff.c

@@ -355,6 +355,24 @@ void __kfree_skb(struct sk_buff *skb)
 	kfree_skbmem(skb);
 }
 
+/**
+ *	kfree_skb - free an sk_buff
+ *	@skb: buffer to free
+ *
+ *	Drop a reference to the buffer and free it if the usage count has
+ *	hit zero.
+ */
+void kfree_skb(struct sk_buff *skb)
+{
+	if (unlikely(!skb))
+		return;
+	if (likely(atomic_read(&skb->users) == 1))
+		smp_rmb();
+	else if (likely(!atomic_dec_and_test(&skb->users)))
+		return;
+	__kfree_skb(skb);
+}
+
 /**
  *	skb_clone	-	duplicate an sk_buff
  *	@skb: buffer to clone
@@ -1799,6 +1817,7 @@ void __init skb_init(void)
 
 EXPORT_SYMBOL(___pskb_trim);
 EXPORT_SYMBOL(__kfree_skb);
+EXPORT_SYMBOL(kfree_skb);
 EXPORT_SYMBOL(__pskb_pull_tail);
 EXPORT_SYMBOL(__alloc_skb);
 EXPORT_SYMBOL(pskb_copy);