[PATCH net-next v2 1/3] net: factor out a helper to decrement the skb refcount

[Paolo Abeni]

The same code is replicated in 3 different places; move it to a
common helper.

Signed-off-by: Paolo Abeni <pab...@redhat.com>
Acked-by: Eric Dumazet <eduma...@google.com>
---
 include/linux/skbuff.h | 13 +++++++++++++
 net/core/datagram.c    |  4 +---
 net/core/skbuff.c      | 14 ++++----------
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 45a59c1..3c25fca 100644
--- 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
index bc46118..e5311a7 100644
--- 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
index 780b7c1..c81b828 100644
--- 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);
 }
-- 
2.9.4