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From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Leonardo Bras <leonardo@linux.ibm.com>, Jens Axboe <axboe@kernel.dk>
Cc: mtk.manpages@gmail.com, linux-man@vger.kernel.org
Subject: Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
Date: Fri, 13 Sep 2019 14:55:06 +0200	[thread overview]
Message-ID: <b65e1f8f-34b4-0db6-bd7a-7b866b29af7a@gmail.com> (raw)
In-Reply-To: <20190801222417.14413-1-leonardo@linux.ibm.com>

Hello Jens,

Would you be willing to take a look at this man-pages bug report
relating to vmsplice()?

Thanks,

Michael

On 8/2/19 12:24 AM, Leonardo Bras wrote:
> As explained in splice.2, SPLICE_F_MOVE became a no-op, and since it
> is needed to use page gifting, it made SPLICE_F_GIFT a no-op too.
> 
> I took a look in current code, and found no use of this flag:
> When enabled, it sets PIPE_BUF_FLAG_GIFT,which is only checked in
> user_page_pipe_buf_steal, which is only used on
> user_page_pipe_buf_ops, as a .steal component.
> 
> But, in the whole kernel code, there is no calling of a steal()
> function, making me believe this flag is not used anymore.
> 
> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
> ---
>  man2/vmsplice.2 | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/man2/vmsplice.2 b/man2/vmsplice.2
> index 17834607b..94fb86142 100644
> --- a/man2/vmsplice.2
> +++ b/man2/vmsplice.2
> @@ -123,6 +123,11 @@ if this flag is not specified, then a subsequent
>  .B SPLICE_F_MOVE
>  must copy the pages.
>  Data must also be properly page aligned, both in memory and length.
> +Starting in Linux 2.6.21, it is a no-op, because the
> +.B SPLICE_F_MOVE
> +also became a no-op on
> +.BR splice (2)
> +.
>  .\" FIXME
>  .\" It looks like the page-alignment requirement went away with
>  .\" commit bd1a68b59c8e3bce45fb76632c64e1e063c3962d
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

       reply	other threads:[~2019-09-13 12:55 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190801222417.14413-1-leonardo@linux.ibm.com>
2019-09-13 12:55 ` Michael Kerrisk (man-pages) [this message]
2019-11-14 18:56   ` [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op Leonardo Bras
2019-12-17 21:12   ` Leonardo Bras
2019-12-18  1:13     ` Jens Axboe
2019-12-18 16:22       ` Leonardo Bras

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