> On Tue, Feb 19 2008, Johann Felix Soden wrote:
> > From: Johann Felix Soden <[EMAIL PROTECTED]>
> >
> > With SPLICE_F_NONBLOCK sys_tee should return number of duplicated bytes,
> > not only -EAGAIN on success.
>
> ?
>
> The current behaviour is to return bytes tee'd, or return -EAGAIN for
> zero bytes if SPLICE_F_NONBLOCK is set. It doesn't return "-EAGAIN on
> success", not sure what you mean there.
>
Sorry, my patch description was not correct.
The new behavior of sys_tee with my patch is:
- return -EAGAIN if there are no data in the pipe, but writer
connected to the pipe,
- return 0 if there are not writers connected
- else return number of duplicated byte
The old behavior was: return -EAGAIN or the number (>0) of duplicated
bytes.
> > This patch also solves the problem, which is described on
> > http://article.gmane.org/gmane.linux.kernel/642502.
> >
> > Signed-off-by: Johann Felix Soden <[EMAIL PROTECTED]>
> > ---
> > fs/splice.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/splice.c b/fs/splice.c
> > index 9b559ee..184fd66 100644
> > --- a/fs/splice.c
> > +++ b/fs/splice.c
> > @@ -1711,7 +1711,7 @@ static long do_tee(struct file *in, struct file *out,
> > size_t len,
> > ret = link_opipe_prep(opipe, flags);
> > if (!ret) {
> > ret = link_pipe(ipipe, opipe, len, flags);
> > - if (!ret && (flags & SPLICE_F_NONBLOCK))
> > + if (ret < 0 && (flags & SPLICE_F_NONBLOCK))
> > ret = -EAGAIN;
> > }
> > }
>
> Perhaps it's just me, but this doesn't make a lot of sense. You override
> any other error with EAGAIN, hm? In fact the only < 0 value that
> link_pipe() will return is -EPIPE, which is perfectly in sync with that
> a pipe write will return if there are no readers attached.
The reason, why I wrote the patch, was, that the example program
mentioned in manpage of tee(2) doesn't stop, if it used like
cat textfile | tee_example outfile | wc because sys_tee returns only
-EAGAIN or the duplicated bytes, not something like EOF.
See also http://article.gmane.org/gmane.linux.kernel/642502.
Patrick McManus described the problem there.
--
Johann Felix Soden
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