Re: [PATCH] sendfile.2: Fix description of the out_fd

["Przemysław Pawełczyk" <przemoc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi,

2011/1/27 Akira Fujita <a-fujita-cUW4a6blu5N8UrSeD/g0lQ@public.gmane.org>:
> commit cc56f7de7f00d188c7c4da1e9861581853b9e92f made
> sendfile(2) can work with any output file.
> Therefore the out_fd of sendfile(2) can refer to any file,
> but current manual (man-pages-3.32) has not been changed so far.

And I thought I was the only one discovering it recently (beside a few
obvious people year ago). :)

> diff -Nrup man-pages-3.32-a/man2/sendfile.2 man-pages-3.32-b/man2/sendfile.2
> --- man-pages-3.32-a/man2/sendfile.2    2010-12-03 16:01:59.000000000 +0900
> +++ man-pages-3.32-b/man2/sendfile.2    2011-01-27 16:03:48.000000000 +0900
> @@ -87,15 +87,11 @@ and the file offset will be updated by t
>  .I count
>  is the number of bytes to copy between the file descriptors.
>
> -Presently (Linux 2.6.9):
> -.IR in_fd ,
> +.IR in_fd
>  must correspond to a file which supports
>  .BR mmap (2)-like
>  operations
> -(i.e., it cannot be a socket);
> -and
> -.I out_fd
> -must refer to a socket.
> +(i.e., it cannot be a socket).

I don't think that completely removing out_fd socket restriction part
is a proper way of fixing this page. Such information should not be
lost.
I would add here sth like:

out_fd was required to be a socket, but since Linux 2.6.33 it can be
any file. If it is a regular file, then sendfile() changes its offset
appropriately.

>
>  Applications may wish to fall back to
>  .BR read (2)/ write (2)
> @@ -168,6 +164,9 @@ In Linux 2.4 and earlier,
>  could refer to a regular file, and

s/could/could also/

>  .BR sendfile ()
>  changed the current offset of that file.

> +Since 2.6.33,
> +.I out_fd
> +can refer to any file.

IMO this change shouldn't be mentioned in NOTES section.

>
>  The original Linux
>  .BR sendfile ()

Regards.

-- 
Przemysław 'Przemoc' Pawełczyk
http://przemoc.net/
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