Commit b32e8fbe authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: tcp_gro_dev_warn() cleanup 



Use DO_ONCE_LITE_IF() and __cold attribute to put tcp_gro_dev_warn()
out of line.

This also allows the message to be printed again after a
"echo 1 > /sys/kernel/debug/clear_warn_once"

Also add a READ_ONCE() when reading device mtu, as it could
be changed concurrently.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231130184135.4130860-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 527d2cd8

net/ipv4/tcp_input.c

+11 −18
Original line number Diff line number Diff line
@@ -202,24 +202,18 @@ static void bpf_skops_established(struct sock *sk, int bpf_op, 
}

#endif



static void tcp_gro_dev_warn(struct sock *sk, const struct sk_buff *skb,

static __cold void tcp_gro_dev_warn(const struct sock *sk, const struct sk_buff *skb,

				    unsigned int len)

{

	static bool __once __read_mostly;



	if (!__once) {

	struct net_device *dev;



		__once = true;



	rcu_read_lock();

	dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);

		if (!dev || len >= dev->mtu)

	if (!dev || len >= READ_ONCE(dev->mtu))

		pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",

			dev ? dev->name : "Unknown driver");

	rcu_read_unlock();

}

}



/* Adapt the MSS value used to make delayed ack decision to the

 * real world.
@@ -250,9 +244,8 @@ static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 
		icsk->icsk_ack.rcv_mss = min_t(unsigned int, len,

					       tcp_sk(sk)->advmss);

		/* Account for possibly-removed options */

		if (unlikely(len > icsk->icsk_ack.rcv_mss +

				   MAX_TCP_OPTION_SPACE))

			tcp_gro_dev_warn(sk, skb, len);

		DO_ONCE_LITE_IF(len > icsk->icsk_ack.rcv_mss + MAX_TCP_OPTION_SPACE,

				tcp_gro_dev_warn, sk, skb, len);

		/* If the skb has a len of exactly 1*MSS and has the PSH bit

		 * set then it is likely the end of an application write. So

		 * more data may not be arriving soon, and yet the data sender