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([2a0d:3344:271a:7310:d5d8:c311:8743:3e10]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a568a7f8f9sm18758020f8f.42.2025.06.19.01.22.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Jun 2025 01:22:38 -0700 (PDT) Message-ID: <10fe50a5-2829-40a2-8741-c67c33898fa6@redhat.com> Date: Thu, 19 Jun 2025 10:22:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net 1/2] tcp_metrics: set maximum cwnd from the dst entry To: Petr Tesarik Cc: "David S. Miller" , Eric Dumazet , Neal Cardwell , Kuniyuki Iwashima , "open list:NETWORKING [TCP]" , David Ahern , Jakub Kicinski , open list References: <20250613102012.724405-1-ptesarik@suse.com> <20250613102012.724405-2-ptesarik@suse.com> <20250617133935.60f621db@mordecai.tesarici.cz> <20250618190124.04b7a2c3@mordecai.tesarici.cz> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250618190124.04b7a2c3@mordecai.tesarici.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/18/25 7:01 PM, Petr Tesarik wrote: > On Tue, 17 Jun 2025 13:39:35 +0200 Petr Tesarik wrote: >> On Tue, 17 Jun 2025 13:00:53 +0200 Paolo Abeni wrote: >>> On 6/13/25 12:20 PM, Petr Tesarik wrote: >>>> diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c >>>> index 4251670e328c8..dd8f3457bd72e 100644 >>>> --- a/net/ipv4/tcp_metrics.c >>>> +++ b/net/ipv4/tcp_metrics.c >>>> @@ -477,6 +477,9 @@ void tcp_init_metrics(struct sock *sk) >>>> if (!dst) >>>> goto reset; >>>> >>>> + if (dst_metric_locked(dst, RTAX_CWND)) >>>> + tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); >>>> + >>>> rcu_read_lock(); >>>> tm = tcp_get_metrics(sk, dst, false); >>>> if (!tm) { >>>> @@ -484,9 +487,6 @@ void tcp_init_metrics(struct sock *sk) >>>> goto reset; >>>> } >>>> >>>> - if (tcp_metric_locked(tm, TCP_METRIC_CWND)) >>>> - tp->snd_cwnd_clamp = tcp_metric_get(tm, TCP_METRIC_CWND); >>>> - >>>> val = READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) ? >>>> 0 : tcp_metric_get(tm, TCP_METRIC_SSTHRESH); >>>> if (val) { >>> >>> It's unclear to me why you drop the tcp_metric_get() here. It looks like >>> the above will cause a functional regression, with unlocked cached >>> metrics no longer taking effects? >> >> Unlocked cached TCP_METRIC_CWND has never taken effects. As you can >> see, tcp_metric_get() was executed only if the metric was locked. Uhm... the locking propagation from dst to tcp storage was not so straight forward to me, I missed it. Please be a little more verbose about this part in the commit message. Thanks, Paolo