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tcp: tcp_gro_dev_warn() cleanup

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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: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231130184135.4130860-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2023-11-30 18:41:35 +00:00 committed by Jakub Kicinski
parent 527d2cd8b8
commit b32e8fbeac
1 changed files with 11 additions and 18 deletions

29
net/ipv4/tcp_input.c

@ -202,23 +202,17 @@ 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,
unsigned int len)
static __cold void tcp_gro_dev_warn(const struct sock *sk, const struct sk_buff *skb,
unsigned int len)
{
static bool __once __read_mostly;
struct net_device *dev;
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)
pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
dev ? dev->name : "Unknown driver");
rcu_read_unlock();
}
rcu_read_lock();
dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);
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
@ -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