Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 5 Jan 2023 23:07:37 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     =?UTF-8?B?6L+Q6L6J5bSU?= <cuiyunhui@bytedance.com>
Cc:     mhiramat@kernel.org, davem@davemloft.net, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com, duanxiongchun@bytedance.com,
        kuniyu@amazon.com, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org
Subject: Re: [External] Re: [PATCH v2] sock: add tracepoint for send recv
 length
Message-ID: <20230105230737.426abfdd@gandalf.local.home>
In-Reply-To: <CAEEQ3wmnUpuZxLbrMwPCk+pnbC27fo4bi-nN-848o6QGO6Xt+Q@mail.gmail.com>
References: <20230105100014.1935-1-cuiyunhui@bytedance.com>
        <20230105090807.51213cea@gandalf.local.home>
        <CAEEQ3wmnUpuZxLbrMwPCk+pnbC27fo4bi-nN-848o6QGO6Xt+Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Precedence: bulk

On Fri, 6 Jan 2023 11:24:18 +0800
运辉崔 <cuiyunhui@bytedance.com> wrote:

> Regardless of whether the MSG_PEEK flag is set or not, it is possible
> to return -errno,
> but based on your suggestion, I plan to modify it like this:
> 
> trace_sock_recvmsg_length(sock->sk, sock->sk->sk_family,
>                           sock->sk->sk_protocol,
>                           !(flags & MSG_PEEK) ? ret : (ret < 0 ? ret : 0),
> 
> what do you think?

Sure.

But note, from your original patch:

> +	trace_sock_recvmsg_length(sock->sk, sock->sk->sk_family,
> +				  sock->sk->sk_protocol,
> +				  (ret > 0 && !(flags & MSG_PEEK)) ?
> +				  ret : 0,
> +				  (ret > 0 && !(flags & MSG_PEEK)) ? 0 : ret,
> +				  flags);

If flags MSG_PEEK is set, you return ret in error regardless, so error
would be ret even if it was positive.

So I'm guessing that this change actually fixed a bug. ;-)

-- Steve