net: factor out a helper to decrement the skb refcount

Paolo Abeni · davem330 · commit 3889a803e1da · 2017-06-12T10:01:29.000-04:00
The same code is replicated in 3 different places; move it to a
common helper.

Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Acked-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
@@ -867,6 +867,19 @@ static inline unsigned int skb_napi_id(const struct sk_buff *skb)
 #endif
 }
 
+/* decrement the reference count and return true if we can free the skb */
+static inline bool skb_unref(struct sk_buff *skb)
+{
+	if (unlikely(!skb))
+		return false;
+	if (likely(atomic_read(&skb->users) == 1))
+		smp_rmb();
+	else if (likely(!atomic_dec_and_test(&skb->users)))
+		return false;
+
+	return true;
+}
+
 void kfree_skb(struct sk_buff *skb);
 void kfree_skb_list(struct sk_buff *segs);
 void skb_tx_error(struct sk_buff *skb);
diff --git a/net/core/datagram.c b/net/core/datagram.c
@@ -330,9 +330,7 @@ void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len)
 {
 	bool slow;
 
-	if (likely(atomic_read(&skb->users) == 1))
-		smp_rmb();
-	else if (likely(!atomic_dec_and_test(&skb->users))) {
+	if (!skb_unref(skb)) {
 		sk_peek_offset_bwd(sk, len);
 		return;
 	}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
@@ -694,12 +694,9 @@ EXPORT_SYMBOL(__kfree_skb);
  */
 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)))
+	if (!skb_unref(skb))
 		return;
+
 	trace_kfree_skb(skb, __builtin_return_address(0));
 	__kfree_skb(skb);
 }
@@ -746,12 +743,9 @@ EXPORT_SYMBOL(skb_tx_error);
  */
 void consume_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)))
+	if (!skb_unref(skb))
 		return;
+
 	trace_consume_skb(skb);
 	__kfree_skb(skb);
 }

Original file line number	Diff line number	Diff line change
`@@ -330,9 +330,7 @@ void __skb_free_datagram_locked(struct sock sk, struct sk_buff skb, int len)`
`330`	`330`	`{`
`331`	`331`	`bool slow;`
`332`	`332`
`333`		`- if (likely(atomic_read(&skb->users) == 1))`
`334`		`- smp_rmb();`
`335`		`- else if (likely(!atomic_dec_and_test(&skb->users))) {`
	`333`	`+ if (!skb_unref(skb)) {`
`336`	`334`	`sk_peek_offset_bwd(sk, len);`
`337`	`335`	`return;`
`338`	`336`	`}`