Commit cc166427 authored Dec 05, 2017 by Willem de Bruijn Committed by David S. Miller Dec 06, 2017

tun: avoid unnecessary READ_ONCE in tun_net_xmit



The statement no longer serves a purpose.

Commit fa35864e ("tuntap: Fix for a race in accessing numqueues")
added the ACCESS_ONCE to avoid a race condition with skb_queue_len.

Commit 436acceb ("tuntap: remove unnecessary sk_receive_queue
length check during xmit") removed the affected skb_queue_len check.

Commit 96f84061 ("tun: add eBPF based queue selection method")
split the function, reading the field a second time in the callee.
The temp variable is now only read once, so just remove it.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent d9b86937

drivers/net/tun.c

+1 −3

Original line number	Original line	Diff line number	Diff line
	@@ -990,14 +990,12 @@ static netdev_tx_t tun_net_xmit(struct sk_buff skb, struct net_device dev)
	struct tun_struct *tun = netdev_priv(dev);		struct tun_struct *tun = netdev_priv(dev);
	int txq = skb->queue_mapping;		int txq = skb->queue_mapping;
	struct tun_file *tfile;		struct tun_file *tfile;
	u32 numqueues = 0;

	rcu_read_lock();		rcu_read_lock();
	tfile = rcu_dereference(tun->tfiles[txq]);		tfile = rcu_dereference(tun->tfiles[txq]);
	numqueues = READ_ONCE(tun->numqueues);

	/* Drop packet if interface is not attached */		/* Drop packet if interface is not attached */
	if (txq >= numqueues)		if (txq >= tun->numqueues)
	goto drop;		goto drop;

	if (!rcu_dereference(tun->steering_prog))		if (!rcu_dereference(tun->steering_prog))

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