This is a note to let you know that I've just added the patch titled
tcp_metrics: optimize tcp_metrics_flush_all()
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp_metrics-optimize-tcp_metrics_flush_all.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9763c1fbc072675f2a24e90a094e26687b4295c9
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Fri Sep 22 22:03:56 2023 +0000
tcp_metrics: optimize tcp_metrics_flush_all()
[ Upstream commit 6532e257aa73645e28dee5b2232cc3c88be62083 ]
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@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index b71f94a5932ac..e0883ba709b0b 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -899,11 +899,13 @@ 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);
@@ -915,6 +917,7 @@ static void tcp_metrics_flush_all(struct net *net)
}
}
spin_unlock_bh(&tcp_metrics_lock);
+ cond_resched();
}
}
