* Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
[not found] <20190801222417.14413-1-leonardo@linux.ibm.com>
@ 2019-09-13 12:55 ` Michael Kerrisk (man-pages)
2019-11-14 18:56 ` Leonardo Bras
2019-12-17 21:12 ` Leonardo Bras
0 siblings, 2 replies; 5+ messages in thread
From: Michael Kerrisk (man-pages) @ 2019-09-13 12:55 UTC (permalink / raw)
To: Leonardo Bras, Jens Axboe; +Cc: mtk.manpages, linux-man
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/
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
2019-09-13 12:55 ` [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op Michael Kerrisk (man-pages)
@ 2019-11-14 18:56 ` Leonardo Bras
2019-12-17 21:12 ` Leonardo Bras
1 sibling, 0 replies; 5+ messages in thread
From: Leonardo Bras @ 2019-11-14 18:56 UTC (permalink / raw)
To: Michael Kerrisk (man-pages), Jens Axboe; +Cc: linux-man
[-- Attachment #1: Type: text/plain, Size: 1676 bytes --]
On Fri, 2019-09-13 at 14:55 +0200, Michael Kerrisk (man-pages) wrote:
> Hello Jens,
>
> Would you be willing to take a look at this man-pages bug report
> relating to vmsplice()?
>
> Thanks,
>
> Michael
Hello Michael, Jens,
Any update about this patch?
Kind Regards,
>
> 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
> >
>
>
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
2019-09-13 12:55 ` [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op Michael Kerrisk (man-pages)
2019-11-14 18:56 ` Leonardo Bras
@ 2019-12-17 21:12 ` Leonardo Bras
2019-12-18 1:13 ` Jens Axboe
1 sibling, 1 reply; 5+ messages in thread
From: Leonardo Bras @ 2019-12-17 21:12 UTC (permalink / raw)
To: Michael Kerrisk (man-pages), Jens Axboe; +Cc: linux-man
[-- Attachment #1: Type: text/plain, Size: 1688 bytes --]
On Fri, 2019-09-13 at 14:55 +0200, Michael Kerrisk (man-pages) wrote:
> Hello Jens,
>
> Would you be willing to take a look at this man-pages bug report
> relating to vmsplice()?
Hello Jens,
Could you please provide feedback on this patch?
Thank you,
Leonardo Bras
>
> 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
> >
>
>
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
2019-12-17 21:12 ` Leonardo Bras
@ 2019-12-18 1:13 ` Jens Axboe
2019-12-18 16:22 ` Leonardo Bras
0 siblings, 1 reply; 5+ messages in thread
From: Jens Axboe @ 2019-12-18 1:13 UTC (permalink / raw)
To: Leonardo Bras, Michael Kerrisk (man-pages); +Cc: linux-man
Sorry, better late than never?
He's right, Nick Piggin removed that flag (and promised to reinstate it,
but a decade later I'm not holding my breath).
On 12/17/19 2:12 PM, Leonardo Bras wrote:
> On Fri, 2019-09-13 at 14:55 +0200, Michael Kerrisk (man-pages) wrote:
>> Hello Jens,
>>
>> Would you be willing to take a look at this man-pages bug report
>> relating to vmsplice()?
>
> Hello Jens,
>
> Could you please provide feedback on this patch?
>
> Thank you,
> Leonardo Bras
>
>
>>
>> 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
>>>
>>
>>
--
Jens Axboe
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op
2019-12-18 1:13 ` Jens Axboe
@ 2019-12-18 16:22 ` Leonardo Bras
0 siblings, 0 replies; 5+ messages in thread
From: Leonardo Bras @ 2019-12-18 16:22 UTC (permalink / raw)
To: Jens Axboe, Michael Kerrisk (man-pages); +Cc: linux-man
[-- Attachment #1: Type: text/plain, Size: 293 bytes --]
On Tue, 2019-12-17 at 18:13 -0700, Jens Axboe wrote:
> Sorry, better late than never?
No problem :)
> He's right, Nick Piggin removed that flag (and promised to reinstate it,
> but a decade later I'm not holding my breath).
Thanks for the feedback!
Best regards,
Leonardo Bras
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-09-13 12:55 ` [PATCH] vmsplice.2: SPLICE_F_GIFT became no-op Michael Kerrisk (man-pages)
2019-11-14 18:56 ` 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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