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tcp: fix MSG_SENDPAGE_NOTLAST logic

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commit 35f9c09fe9 (tcp: tcp_sendpages() should call tcp_push() once)
added an internal flag : MSG_SENDPAGE_NOTLAST meant to be set on all
frags but the last one for a splice() call.

The condition used to set the flag in pipe_to_sendpage() relied on
splice() user passing the exact number of bytes present in the pipe,
or a smaller one.

But some programs pass an arbitrary high value, and the test fails.

The effect of this bug is a lack of tcp_push() at the end of a
splice(pipe -> socket) call, and possibly very slow or erratic TCP
sessions.

We should both test sd->total_len and fact that another fragment
is in the pipe (pipe->nrbufs > 1)

Many thanks to Willy for providing very clear bug report, bisection
and test programs.

Reported-by: Willy Tarreau <w@1wt.eu>
Bisected-by: Willy Tarreau <w@1wt.eu>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-01-06 18:21:49 +00:00 committed by David S. Miller
parent 9dd4a13a89
commit ae62ca7b03
1 changed files with 3 additions and 1 deletions
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4
fs/splice.c
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@ -696,8 +696,10 @@ static int pipe_to_sendpage(struct pipe_inode_info *pipe,
return -EINVAL;
more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
if (sd->len < sd->total_len)
if (sd->len < sd->total_len && pipe->nrbufs > 1)
more |= MSG_SENDPAGE_NOTLAST;
return file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}