| From | Paul Gortmaker <> | Subject | [v2.6.34-stable 041/213] tcp: fix MSG_SENDPAGE_NOTLAST logic | Date | Wed, 5 Feb 2014 14:59:56 -0500 |
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From: Eric Dumazet <edumazet@google.com>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. -------------------
commit ae62ca7b03217be5e74759dc6d7698c95df498b3 upstream.
commit 35f9c09fe9c72e (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> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- fs/splice.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/splice.c b/fs/splice.c index 3bec7c63be64..1c991d6a64b4 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -640,8 +640,10 @@ static int pipe_to_sendpage(struct pipe_inode_info *pipe, ret = buf->ops->confirm(pipe, buf); if (!ret) { 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; + if (file->f_op && file->f_op->sendpage) ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len, &pos, more); -- 1.8.5.2
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