linux-kernel - Re: [PATCH v2] man2/splice.2: document SPLICE_F

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Message-ID: <zt5lslryl7gr6qvuahpuziodcvh3rd6qw5pbxx2m6rinmn6yrz@xt46qxmtknen>
Date:   Wed, 27 Sep 2023 13:29:23 +0200
From:   Alejandro Colomar <alx@...nel.org>
To:     Max Kellermann <max.kellermann@...os.com>
Cc:     linux-man@...r.kernel.org, brauner@...nel.org, axboe@...nel.dk,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        libc-alpha@...rceware.org
Subject: Re: [PATCH v2] man2/splice.2: document SPLICE_F_NOWAIT

Hi Max,

On Tue, Sep 26, 2023 at 03:43:39PM +0200, Max Kellermann wrote:
> Patch for SPLICE_F_NOWAIT submitted to LKML:
>  https://lore.kernel.org/lkml/20230926063609.2451260-1-max.kellermann@ionos.com/
> 
> In the HISTORY section, I declared Linux 6.7 as the first version to
> have this feature, but this is only speculation, because
> SPLICE_F_NOWAIT is still under discussion and has not yet been merged.
> 
> Signed-off-by: Max Kellermann <max.kellermann@...os.com>

Thanks for the patch.  It LGTM.  Please ping when the kernel patch is
merged or something.

Thanks,
Alex

> ---
>  man2/splice.2 | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/splice.2 b/man2/splice.2
> index e9a18e668..a07c001ac 100644
> --- a/man2/splice.2
> +++ b/man2/splice.2
> @@ -89,13 +89,26 @@ call);
>  in the future, a correct implementation may be restored.
>  .TP
>  .B SPLICE_F_NONBLOCK
> -Do not block on I/O.
> +Do not block on I/O on pipes.
>  This makes the splice pipe operations nonblocking, but
>  .BR splice ()
>  may nevertheless block because the file descriptors that
>  are spliced to/from may block (unless they have the
>  .B O_NONBLOCK
> -flag set).
> +flag set or
> +.B SPLICE_F_NOWAIT
> +is specified).
> +.TP
> +.B SPLICE_F_NOWAIT
> +If no data is immediately available on
> +.I fd_in
> +and it is not a pipe, do not wait (e.g. for backing storage or locks),
> +but return immediately with
> +.B EAGAIN.
> +This is analogous to the
> +.B RWF_NOWAIT
> +flag of
> +.BR preadv2 ().
>  .TP
>  .B SPLICE_F_MORE
>  More data will be coming in a subsequent splice.
> @@ -138,6 +151,8 @@ is set to indicate the error.
>  .TP
>  .B EAGAIN
>  .B SPLICE_F_NONBLOCK
> +or
> +.B SPLICE_F_NOWAIT
>  was specified in
>  .I flags
>  or one of the file descriptors had been marked as nonblocking
> @@ -192,6 +207,9 @@ was required to be a pipe.
>  Since Linux 2.6.31,
>  .\" commit 7c77f0b3f9208c339a4b40737bb2cb0f0319bb8d
>  both arguments may refer to pipes.
> +.PP
> +.B SPLICE_F_NOWAIT
> +was added in Linux 6.7.
>  .SH NOTES
>  The three system calls
>  .BR splice (),
> -- 
> 2.39.2
> 

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