Re: [PATCH] splice support #2

[Jens Axboe <axboe@suse.de>]

On Tue, Apr 04 2006, Andy Lutomirski wrote:
> Jens Axboe wrote:
> >On Fri, Mar 31 2006, Linus Torvalds wrote:
> >
> >>
> >>On Fri, 31 Mar 2006, Jens Axboe wrote:
> >>
> >>>> ssize_t psplice(int fdin, int fdout, size_t len, off_t ofs, unsigned 
> >>>> flags);
> >>>
> >>>I definitely see some valid reasons for adding a file offset instead of
> >>>using ->f_pos, I'll leave that decision up to Linus though. Linus?
> >>
> >>I think a file offset is fine, the one thing holding me back was just the 
> >>interface. One file offset per fd? Or just have the rule that the file 
> >>offset is for the "non-pipe" device?
> >
> >
> >Intuitively, I'd expect the offset to be tied to the non-pipe if I were
> >to eg see this for the first time. So my vote would go for that.
> >
> 
> Eee!  That means that splice(file_fd, pipe_fd, 1000) and splice(pipe_fd, 
> file_fd, 1000) have different semantics.  It also would seem to prevent 
> ever implementing direct file-to-file splicing.

The semantics as written: (fdin, fdout, len). But yes the offset gets
ugly, unless you add two offsets. And you are right it would not go well
with file -> file splicing, which btw is already implemented (just not
in 2.6.17-rc1) along with file -> socket.

-- 
Jens Axboe