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

[Akira Fujita <a-fujita-cUW4a6blu5N8UrSeD/g0lQ@public.gmane.org>]

Hello Michael,

Thank you for your work!

Regards,
Akira Fujita

(2011/09/12 1:00), Michael Kerrisk wrote:
> Hello Akira,
> 
> 2011/3/9 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.
> 
> Thank you for this report! Some notes below.
> 
>> Signed-off-by: Akira Fujita<a-fujita-cUW4a6blu5N8UrSeD/g0lQ@public.gmane.org>
>> ---
>>   sendfile.2 |   16 +++++++++-------
>>   1 file changed, 9 insertions(+), 7 deletions(-)
>> --- man-pages-3.32-a/man2/sendfile.2    2010-12-03 16:01:59.000000000 +0900
>> +++ man-pages-3.32-b/man2/sendfile.2    2011-03-09 10:34:53.000000000 +0900
>> @@ -87,15 +87,17 @@ 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);
> 
> You removed that piece, but I believe nothing changed for 'in_fd', so
> I kept that piece.
> 
>> -and
>> -.I out_fd
>> -must refer to a socket.
>> +(i.e., it cannot be a socket).
>> +
>> +.IR 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
>> +.BR sendfile()
>> +changes its offset appropriately.
>>
>>   Applications may wish to fall back to
>>   .BR read (2)/ write (2)
>> @@ -165,7 +167,7 @@ to minimize the number of packets and to
>>
>>   In Linux 2.4 and earlier,
>>   .I out_fd
>> -could refer to a regular file, and
>> +could also refer to a regular file, and
>>   .BR sendfile ()
>>   changed the current offset of that file.
> 
> For 3.33 I applied a slightly modified version of you patch; see below.
> 
> Cheers,
> 
> Michael
> 
> --- a/man2/sendfile.2
> +++ b/man2/sendfile.2
> @@ -92,10 +92,14 @@ The
>   argument must correspond to a file which supports
>   .BR mmap (2)-like
>   operations
> -(i.e., it cannot be a socket);
> -and
> +(i.e., it cannot be a socket).
> +In Linux kernels before 2.6.33,
>   .I out_fd
>   must refer to a socket.
> +Since Linux 2.6.33 it can be any file.
> +If it is a regular file, then
> +.BR sendfile()
> +changes the file offset offset appropriately.
> 
>   Applications may wish to fall back to
>   .BR read (2)/ write (2)
> @@ -165,7 +169,7 @@ to minimize the number of packets and to tune performance.
> 
>   In Linux 2.4 and earlier,
>   .I out_fd
> -could refer to a regular file, and
> +could also refer to a regular file, and
>   .BR sendfile ()
>   changed the current offset of that file.
> 
> 
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