On Wed, Feb 20, 2008 at 10:35:28AM +0100, Jens Axboe wrote:
> On Tue, Feb 19 2008, Johann Felix Soden wrote:
> >
> > Am Dienstag, den 19.02.2008, 22:25 +0100 schrieb Jens Axboe:
> > > On Tue, Feb 19 2008, Johann Felix Soden wrote:
> > > > > 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.
> > >
> > > Your patch has an odd way of achieving that goal, modify the real
> > > location of the assignment instead of overriding something. That has the
> > > potential to turn into another confusing bug later on, wondering why the
> > > heck your return value isn't being passed back.
> > >
> > > Improvement is welcome though, you can't distuingish -EAGAIN on the
> > > input side from the output side currently.
> > >
> When non-blocking is set, ideally we want to return 0 if there's no hope
> of anymore data and EAGAIN if trying later may yield some data. So how
> about this instead?
>
> diff --git a/fs/splice.c b/fs/splice.c
> index 9b559ee..0670c91 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1669,6 +1669,13 @@ static int link_pipe(struct pipe_inode_info *ipipe,
> i++;
> } while (len);
>
> + /*
> + * return EAGAIN if we have the potential of some data in the
> + * future, otherwise just return 0
> + */
> + if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
> + ret = -EAGAIN;
> +
> inode_double_unlock(ipipe->inode, opipe->inode);
>
> /*
> @@ -1709,11 +1716,8 @@ static long do_tee(struct file *in, struct file *out,
> size_t len,
> ret = link_ipipe_prep(ipipe, flags);
> if (!ret) {
> ret = link_opipe_prep(opipe, flags);
> - if (!ret) {
> + if (!ret)
> ret = link_pipe(ipipe, opipe, len, flags);
> - if (!ret && (flags & SPLICE_F_NONBLOCK))
> - ret = -EAGAIN;
> - }
> }
> }
>
Thanks! This works great.
Add if you want: Tested-by: Johann Felix Soden <[EMAIL PROTECTED]>
---
Johann Felix Soden
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