netdev - Re: [PATCH net-next v14 4/9] net: devmem: Implement TX path

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Message-ID: <085a78fc-acfc-4a86-9dbf-18795ad68b4c@redhat.com>
Date: Tue, 13 May 2025 11:12:04 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 io-uring@...r.kernel.org, virtualization@...ts.linux.dev,
 kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc: Donald Hunter <donald.hunter@...il.com>, Jakub Kicinski
 <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
 Jonathan Corbet <corbet@....net>, Andrew Lunn <andrew+netdev@...n.ch>,
 Jeroen de Borst <jeroendb@...gle.com>,
 Harshitha Ramamurthy <hramamurthy@...gle.com>,
 Kuniyuki Iwashima <kuniyu@...zon.com>, Willem de Bruijn
 <willemb@...gle.com>, Jens Axboe <axboe@...nel.dk>,
 Pavel Begunkov <asml.silence@...il.com>, David Ahern <dsahern@...nel.org>,
 Neal Cardwell <ncardwell@...gle.com>, "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Stefan Hajnoczi <stefanha@...hat.com>,
 Stefano Garzarella <sgarzare@...hat.com>, Shuah Khan <shuah@...nel.org>,
 sdf@...ichev.me, dw@...idwei.uk, Jamal Hadi Salim <jhs@...atatu.com>,
 Victor Nogueira <victor@...atatu.com>, Pedro Tammela
 <pctammela@...atatu.com>, Samiullah Khawaja <skhawaja@...gle.com>,
 Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [PATCH net-next v14 4/9] net: devmem: Implement TX path

On 5/8/25 2:48 AM, Mina Almasry wrote:
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 86c427f166367..0ae265d39184e 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1059,6 +1059,7 @@ int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
>  
>  int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
>  {
> +	struct net_devmem_dmabuf_binding *binding = NULL;
>  	struct tcp_sock *tp = tcp_sk(sk);
>  	struct ubuf_info *uarg = NULL;
>  	struct sk_buff *skb;
> @@ -1066,11 +1067,23 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
>  	int flags, err, copied = 0;
>  	int mss_now = 0, size_goal, copied_syn = 0;
>  	int process_backlog = 0;
> +	bool sockc_valid = true;
>  	int zc = 0;
>  	long timeo;
>  
>  	flags = msg->msg_flags;
>  
> +	sockc = (struct sockcm_cookie){ .tsflags = READ_ONCE(sk->sk_tsflags) };
> +	if (msg->msg_controllen) {
> +		err = sock_cmsg_send(sk, msg, &sockc);
> +		if (unlikely(err))
> +			/* Don't return error until MSG_FASTOPEN has been
> +			 * processed; that may succeed even if the cmsg is
> +			 * invalid.
> +			 */
> +			sockc_valid = false;

It occurred to me a bit too late that this chunk of code could be
cleaned-up a bit using a 'sockc_err' variable to store the
sock_cmsg_send() return code instead of the 'sockc_valid' bool. It
should avoid a conditional here and in the later error check.

(just to mention a possible follow-up! no need to repost!)

Thanks,

Paolo