linux-kernel - Re: [External] Re: [PATCH v2] sock: add tracepoint for send recv length

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Message-ID: <20230105230737.426abfdd@gandalf.local.home>
Date:   Thu, 5 Jan 2023 23:07:37 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     运辉崔 <cuiyunhui@...edance.com>
Cc:     mhiramat@...nel.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, duanxiongchun@...edance.com,
        kuniyu@...zon.com, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v2] sock: add tracepoint for send recv
 length

On Fri, 6 Jan 2023 11:24:18 +0800
运辉崔 <cuiyunhui@...edance.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