linux-kernel - Re: [PATCH] move_pages.2: not return ENOENT if the page are already on the target nodes

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Date:   Mon, 30 Dec 2019 18:49:29 -0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     John Hubbard <jhubbard@...dia.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        cl@...ux.com, mhocko@...e.com, cai@....pw,
        akpm@...ux-foundation.org
Cc:     linux-man@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] move_pages.2: not return ENOENT if the page are already
 on the target nodes



On 12/17/19 11:36 PM, John Hubbard wrote:
> On 12/13/19 5:55 PM, Michael Kerrisk (man-pages) wrote:
> ...
>>>> whoa, hold on. If I'm reading through the various error paths
>>>> correctly, then this
>>>> code is *never* going to return ENOENT for the whole function. It can
>>>> fill in that
>>>> value per-page, in the status array, but that's all. Did I get that
>>>> right?
>>>
>>> Nice catch. Yes, you are right.
>>>
>>>>
>>>> If so, we need to redo this part of the man page.
>>>
>>> Yes.
>>
>> So where are things at with this? Is an improved man-pages
>> patch on the way, or is some other action (on the API) planned?
>>
>
> I was waiting to see if Yang was going to respond...anyway, I think
> we're looking at approximately this sort of change:
>

Hi John,

I apologize for the delay, just came back from vacation. Thanks for 
taking care of the patch.

> diff --git a/man2/move_pages.2 b/man2/move_pages.2
> index 2d96468fa..1bf1053f2 100644
> --- a/man2/move_pages.2
> +++ b/man2/move_pages.2
> @@ -191,12 +191,6 @@ was specified or an attempt was made to migrate 
> pages of a kernel thread.
>  .B ENODEV
>  One of the target nodes is not online.
>  .TP
> -.B ENOENT
> -No pages were found that require moving.
> -All pages are either already
> -on the target node, not present, had an invalid address or could not be
> -moved because they were mapped by multiple processes.
> -.TP
>  .B EPERM
>  The caller specified
>  .B MPOL_MF_MOVE_ALL
>
> ...But I'm not sure if we should change the implementation, instead, so
> that it *can* return ENOENT. That's the main question to resolve before
> creating any more patches, I think.
>
> In addition, Michal mentioned that the page states in the status array 
> also
> need updated documentation.
>
>
> thanks,