netdev - Re: Splice status

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Message-ID: <AANLkTikciGxxTR2a2aEASVxPp4PaHWV0BcyIPMLmRsgh@mail.gmail.com>
Date:	Mon, 5 Jul 2010 20:08:25 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Ofer Heifetz <oferh@...vell.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Splice status

On Mon, Jul 5, 2010 at 6:52 PM, Ofer Heifetz <oferh@...vell.com> wrote:
> I am using Samba, so from my understanding of the source code, it loops and performs splice(sock, pipe) and splice(pipe, fd). There is no flush of any sort in between.
>

I checked the function: sys_recvfile() and found It is buggy.

                to_write = nread;
                while (to_write > 0) {
                        int thistime;
                        thistime = splice(pipefd[0], NULL, tofd,
                                          &splice_offset, to_write,
                                          SPLICE_F_MOVE);
                        if (thistime == -1) {
                                goto done;
                        }
                        to_write -= thistime;
                }

                total_written += nread;
                count -= nread;

When splice fails, it should drain the pipe. If not, the following
splice(2) to pipe may hang, because the pipe hasn't enough space for
the data read from socket.

> When you say drain you mean to flush all data to pipe?
>

No. I means to read all the data in the pipe.


-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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