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tcp_metrics: optimize tcp_metrics_flush_all()

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This is inspired by several syzbot reports where
tcp_metrics_flush_all() was seen in the traces.

We can avoid acquiring tcp_metrics_lock for empty buckets,
and we should add one cond_resched() to break potential long loops.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Eric Dumazet 2023-09-22 22:03:56 +00:00 committed by Paolo Abeni
parent a135798e6e
commit 6532e257aa
1 changed files with 5 additions and 2 deletions
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7
net/ipv4/tcp_metrics.c
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@ -898,11 +898,13 @@ static void tcp_metrics_flush_all(struct net *net)
unsigned int row;
for (row = 0; row < max_rows; row++, hb++) {
struct tcp_metrics_block __rcu **pp;
struct tcp_metrics_block __rcu **pp = &hb->chain;
bool match;
if (!rcu_access_pointer(*pp))
continue;
spin_lock_bh(&tcp_metrics_lock);
pp = &hb->chain;
for (tm = deref_locked(*pp); tm; tm = deref_locked(*pp)) {
match = net ? net_eq(tm_net(tm), net) :
!refcount_read(&tm_net(tm)->ns.count);
@ -914,6 +916,7 @@ static void tcp_metrics_flush_all(struct net *net)
}
}
spin_unlock_bh(&tcp_metrics_lock);
cond_resched();
}
}