net: qdisc: use rcu prefix and silence sparse warnings

Add __rcu notation to qdisc handling by doing this we can make
smatch output more legible. And anyways some of the cases should
be using rcu_dereference() see qdisc_all_tx_empty(),
qdisc_tx_chainging(), and so on.

Also *wake_queue() API is commonly called from driver timer routines
without rcu lock or rtnl lock. So I added rcu_read_lock() blocks
around netif_wake_subqueue and netif_tx_wake_queue.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 49 insertions, 2 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 3c6a967e5830..b3d6dbc0c696 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2177,6 +2177,53 @@ static struct dev_kfree_skb_cb *get_kfree_skb_cb(const struct sk_buff *skb)
         return (struct dev_kfree_skb_cb *)skb->cb;
 }
 
+void netif_schedule_queue(struct netdev_queue *txq)
+{
+        rcu_read_lock();
+        if (!(txq->state & QUEUE_STATE_ANY_XOFF)) {
+                struct Qdisc *q = rcu_dereference(txq->qdisc);
+
+                __netif_schedule(q);
+        }
+        rcu_read_unlock();
+}
+EXPORT_SYMBOL(netif_schedule_queue);
+
+/**
+ *      netif_wake_subqueue - allow sending packets on subqueue
+ *      @dev: network device
+ *      @queue_index: sub queue index
+ *
+ * Resume individual transmit queue of a device with multiple transmit queues.
+ */
+void netif_wake_subqueue(struct net_device *dev, u16 queue_index)
+{
+        struct netdev_queue *txq = netdev_get_tx_queue(dev, queue_index);
+
+        if (test_and_clear_bit(__QUEUE_STATE_DRV_XOFF, &txq->state)) {
+                struct Qdisc *q;
+
+                rcu_read_lock();
+                q = rcu_dereference(txq->qdisc);
+                __netif_schedule(q);
+                rcu_read_unlock();
+        }
+}
+EXPORT_SYMBOL(netif_wake_subqueue);
+
+void netif_tx_wake_queue(struct netdev_queue *dev_queue)
+{
+        if (test_and_clear_bit(__QUEUE_STATE_DRV_XOFF, &dev_queue->state)) {
+                struct Qdisc *q;
+
+                rcu_read_lock();
+                q = rcu_dereference(dev_queue->qdisc);
+                __netif_schedule(q);
+                rcu_read_unlock();
+        }
+}
+EXPORT_SYMBOL(netif_tx_wake_queue);
+
 void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
 {
         unsigned long flags;
@@ -3432,7 +3479,7 @@ static int ing_filter(struct sk_buff *skb, struct netdev_queue *rxq)
         skb->tc_verd = SET_TC_RTTL(skb->tc_verd, ttl);
         skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_INGRESS);
 
-        q = rxq->qdisc;
+        q = rcu_dereference(rxq->qdisc);
         if (q != &noop_qdisc) {
                 spin_lock(qdisc_lock(q));
                 if (likely(!test_bit(__QDISC_STATE_DEACTIVATED, &q->state)))
@@ -3449,7 +3496,7 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
 {
         struct netdev_queue *rxq = rcu_dereference(skb->dev->ingress_queue);
 
-        if (!rxq || rxq->qdisc == &noop_qdisc)
+        if (!rxq || rcu_access_pointer(rxq->qdisc) == &noop_qdisc)
                 goto out;
 
         if (*pt_prev) {