netdev - [PATCH v4 net-next 4/9] net: core: Another step of skb receive list processing

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Message-ID: <eed0dd67-8826-edec-7463-138b60d8f73e@solarflare.com>
Date:   Mon, 2 Jul 2018 16:13:24 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH v4 net-next 4/9] net: core: Another step of skb receive list
 processing

netif_receive_skb_list_internal() now processes a list and hands it
 on to the next function.

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 net/core/dev.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 56 insertions(+), 5 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 99167ff83919..d7f2a880aeed 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4729,6 +4729,14 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_bpf *xdp)
 	return ret;
 }
 
+static void __netif_receive_skb_list(struct list_head *head)
+{
+	struct sk_buff *skb, *next;
+
+	list_for_each_entry_safe(skb, next, head, list)
+		__netif_receive_skb(skb);
+}
+
 static int netif_receive_skb_internal(struct sk_buff *skb)
 {
 	int ret;
@@ -4769,6 +4777,50 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
 	return ret;
 }
 
+static void netif_receive_skb_list_internal(struct list_head *head)
+{
+	struct bpf_prog *xdp_prog = NULL;
+	struct sk_buff *skb, *next;
+
+	list_for_each_entry_safe(skb, next, head, list) {
+		net_timestamp_check(netdev_tstamp_prequeue, skb);
+		if (skb_defer_rx_timestamp(skb))
+			/* Handled, remove from list */
+			list_del(&skb->list);
+	}
+
+	if (static_branch_unlikely(&generic_xdp_needed_key)) {
+		preempt_disable();
+		rcu_read_lock();
+		list_for_each_entry_safe(skb, next, head, list) {
+			xdp_prog = rcu_dereference(skb->dev->xdp_prog);
+			if (do_xdp_generic(xdp_prog, skb) != XDP_PASS)
+				/* Dropped, remove from list */
+				list_del(&skb->list);
+		}
+		rcu_read_unlock();
+		preempt_enable();
+	}
+
+	rcu_read_lock();
+#ifdef CONFIG_RPS
+	if (static_key_false(&rps_needed)) {
+		list_for_each_entry_safe(skb, next, head, list) {
+			struct rps_dev_flow voidflow, *rflow = &voidflow;
+			int cpu = get_rps_cpu(skb->dev, skb, &rflow);
+
+			if (cpu >= 0) {
+				enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
+				/* Handled, remove from list */
+				list_del(&skb->list);
+			}
+		}
+	}
+#endif
+	__netif_receive_skb_list(head);
+	rcu_read_unlock();
+}
+
 /**
  *	netif_receive_skb - process receive buffer from network
  *	@skb: buffer to process
@@ -4796,20 +4848,19 @@ EXPORT_SYMBOL(netif_receive_skb);
  *	netif_receive_skb_list - process many receive buffers from network
  *	@head: list of skbs to process.
  *
- *	For now, just calls netif_receive_skb() in a loop, ignoring the
- *	return value.
+ *	Since return value of netif_receive_skb() is normally ignored, and
+ *	wouldn't be meaningful for a list, this function returns void.
  *
  *	This function may only be called from softirq context and interrupts
  *	should be enabled.
  */
 void netif_receive_skb_list(struct list_head *head)
 {
-	struct sk_buff *skb, *next;
+	struct sk_buff *skb;
 
 	list_for_each_entry(skb, head, list)
 		trace_netif_receive_skb_list_entry(skb);
-	list_for_each_entry_safe(skb, next, head, list)
-		netif_receive_skb_internal(skb);
+	netif_receive_skb_list_internal(head);
 }
 EXPORT_SYMBOL(netif_receive_skb_list);