net: fix problem in dequeuing from input_pkt_queue

Fix some issues introduced in batch skb dequeuing for input_pkt_queue.
The primary issue it that the queue head must be incremented only
after a packet has been processed, that is only after
__netif_receive_skb has been called.  This is needed for the mechanism
to prevent OOO packet in RFS.  Also when flushing the input_pkt_queue
and process_queue, the process queue should be done first to prevent
OOO packets.

Because the input_pkt_queue has been effectively split into two queues,
the calculation of the tail ptr is no longer correct.  The correct value
would be head+input_pkt_queue->len+process_queue->len.  To avoid
this calculation we added an explict input_queue_tail in softnet_data.
The tail value is simply incremented when queuing to input_pkt_queue.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 13 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 6c820650b80f..0aab66d68b19 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2426,10 +2426,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
                 if (skb_queue_len(&sd->input_pkt_queue)) {
 enqueue:
                         __skb_queue_tail(&sd->input_pkt_queue, skb);
-#ifdef CONFIG_RPS
-                        *qtail = sd->input_queue_head +
-                                        skb_queue_len(&sd->input_pkt_queue);
-#endif
+                        input_queue_tail_incr_save(sd, qtail);
                         rps_unlock(sd);
                         local_irq_restore(flags);
                         return NET_RX_SUCCESS;
@@ -2964,7 +2961,7 @@ static void flush_backlog(void *arg)
                 if (skb->dev == dev) {
                         __skb_unlink(skb, &sd->input_pkt_queue);
                         kfree_skb(skb);
-                        input_queue_head_add(sd, 1);
+                        input_queue_head_incr(sd);
                 }
         }
         rps_unlock(sd);
@@ -2973,6 +2970,7 @@ static void flush_backlog(void *arg)
                 if (skb->dev == dev) {
                         __skb_unlink(skb, &sd->process_queue);
                         kfree_skb(skb);
+                        input_queue_head_incr(sd);
                 }
         }
 }
@@ -3328,18 +3326,20 @@ static int process_backlog(struct napi_struct *napi, int quota)
                 while ((skb = __skb_dequeue(&sd->process_queue))) {
                         local_irq_enable();
                         __netif_receive_skb(skb);
-                        if (++work >= quota)
-                                return work;
                         local_irq_disable();
+                        input_queue_head_incr(sd);
+                        if (++work >= quota) {
+                                local_irq_enable();
+                                return work;
+                        }
                 }
 
                 rps_lock(sd);
                 qlen = skb_queue_len(&sd->input_pkt_queue);
-                if (qlen) {
-                        input_queue_head_add(sd, qlen);
+                if (qlen)
                         skb_queue_splice_tail_init(&sd->input_pkt_queue,
                                                    &sd->process_queue);
-                }
+
                 if (qlen < quota - work) {
                         /*
                          * Inline a custom version of __napi_complete().
@@ -5679,12 +5679,14 @@ static int dev_cpu_callback(struct notifier_block *nfb,
         local_irq_enable();
 
         /* Process offline CPU's input_pkt_queue */
-        while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
+        while ((skb = __skb_dequeue(&oldsd->process_queue))) {
                 netif_rx(skb);
-                input_queue_head_add(oldsd, 1);
+                input_queue_head_incr(oldsd);
         }
-        while ((skb = __skb_dequeue(&oldsd->process_queue)))
+        while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
                 netif_rx(skb);
+                input_queue_head_incr(oldsd);
+        }
 
         return NOTIFY_OK;
 }