net: introduce dev_consume_skb_any()

Some network drivers use dev_kfree_skb_any() and dev_kfree_skb_irq()
helpers to free skbs, both for dropped packets and TX completed ones.

We need to separate the two causes to get better diagnostics
given by dropwatch or "perf record -e skb:kfree_skb"

This patch provides two new helpers, dev_consume_skb_any() and
dev_consume_skb_irq() to be used for consumed skbs.

__dev_kfree_skb_irq() is slightly optimized to remove one
atomic_dec_and_test() in fast path, and use this_cpu_{r|w} accessors.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 44 insertions, 9 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7f0ed423a360..9d55e5188b96 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2368,17 +2368,52 @@ static inline int netif_copy_real_num_queues(struct net_device *to_dev,
 #define DEFAULT_MAX_NUM_RSS_QUEUES      (8)
 int netif_get_num_default_rss_queues(void);
 
-/* Use this variant when it is known for sure that it
- * is executing from hardware interrupt context or with hardware interrupts
- * disabled.
- */
-void dev_kfree_skb_irq(struct sk_buff *skb);
+enum skb_free_reason {
+        SKB_REASON_CONSUMED,
+        SKB_REASON_DROPPED,
+};
+
+void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason);
+void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason);
 
-/* Use this variant in places where it could be invoked
- * from either hardware interrupt or other context, with hardware interrupts
- * either disabled or enabled.
+/*
+ * It is not allowed to call kfree_skb() or consume_skb() from hardware
+ * interrupt context or with hardware interrupts being disabled.
+ * (in_irq() || irqs_disabled())
+ *
+ * We provide four helpers that can be used in following contexts :
+ *
+ * dev_kfree_skb_irq(skb) when caller drops a packet from irq context,
+ *  replacing kfree_skb(skb)
+ *
+ * dev_consume_skb_irq(skb) when caller consumes a packet from irq context.
+ *  Typically used in place of consume_skb(skb) in TX completion path
+ *
+ * dev_kfree_skb_any(skb) when caller doesn't know its current irq context,
+ *  replacing kfree_skb(skb)
+ *
+ * dev_consume_skb_any(skb) when caller doesn't know its current irq context,
+ *  and consumed a packet. Used in place of consume_skb(skb)
  */
-void dev_kfree_skb_any(struct sk_buff *skb);
+static inline void dev_kfree_skb_irq(struct sk_buff *skb)
+{
+        __dev_kfree_skb_irq(skb, SKB_REASON_DROPPED);
+}
+
+static inline void dev_consume_skb_irq(struct sk_buff *skb)
+{
+        __dev_kfree_skb_irq(skb, SKB_REASON_CONSUMED);
+}
+
+static inline void dev_kfree_skb_any(struct sk_buff *skb)
+{
+        __dev_kfree_skb_any(skb, SKB_REASON_DROPPED);
+}
+
+static inline void dev_consume_skb_any(struct sk_buff *skb)
+{
+        __dev_kfree_skb_any(skb, SKB_REASON_CONSUMED);
+}
 
 int netif_rx(struct sk_buff *skb);
 int netif_rx_ni(struct sk_buff *skb);