Subject: Re: [RFC v2 02/19] skbuff: pass a struct ubuf_info in msghdr
To:     Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Willem de Bruijn <willemb@google.com>,
        Eric Dumazet <edumazet@google.com>,
        David Ahern <dsahern@kernel.org>, Jens Axboe <axboe@kernel.dk>
References: <cover.1640029579.git.asml.silence@gmail.com>
 <7dae2f61ee9a1ad38822870764fcafad43a3fe4e.1640029579.git.asml.silence@gmail.com>
From:   Hao Xu <haoxu@linux.alibaba.com>
Message-ID: <fd376342-13e2-4ce9-074a-f6b3da69be3b@linux.alibaba.com>
Date:   Tue, 11 Jan 2022 21:51:55 +0800
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在 2021/12/21 下午11:35, Pavel Begunkov 写道:
> Instead of the net stack managing ubuf_info, allow to pass it in from
> outside in a struct msghdr (in-kernel structure), so io_uring can make
> use of it.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
Hi Pavel,
I've some confusions here since I have a lack of
network knowledge.
The first one is why do we make ubuf_info visible
for io_uring. Why not just follow the old MSG_ZEROCOPY
logic?

The second one, my understanding about the buffer
lifecycle is that the kernel side informs
the userspace by a cqe generated by the ubuf_info
callback that all the buffers attaching to the
same notifier is now free to use when all the data
is sent, then why is the flush in 13/19 needed as
it is at the submission period?

Regards,
Hao