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Subject: Re: [PATCH] move_pages.2: not return ENOENT if the page are already
 on the target nodes
To:     John Hubbard <jhubbard@nvidia.com>, mtk.manpages@gmail.com,
        cl@linux.com, mhocko@suse.com, cai@lca.pw,
        akpm@linux-foundation.org
Cc:     linux-man@vger.kernel.org, linux-api@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <1575596090-115377-1-git-send-email-yang.shi@linux.alibaba.com>
 <0dc96e40-5f2b-a2fe-6e5f-b6f3d5e9ebde@nvidia.com>
From:   Yang Shi <yang.shi@linux.alibaba.com>
Message-ID: <95170ea5-5b62-9168-fcd9-93b43330a1b4@linux.alibaba.com>
Date:   Fri, 6 Dec 2019 09:26:05 -0800
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On 12/6/19 12:25 AM, John Hubbard wrote:
> On 12/5/19 5:34 PM, Yang Shi wrote:
>> Since commit e78bbfa82624 ("mm: stop returning -ENOENT
>> from sys_move_pages() if nothing got migrated"), move_pages doesn't
>> return -ENOENT anymore if the pages are already on the target nodes, but
>> this change is never reflected in manpage.
>>
>> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
>> Cc: Christoph Lameter <cl@linux.com>
>> Cc: John Hubbard <jhubbard@nvidia.com>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Qian Cai <cai@lca.pw>
>> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
>> ---
>>   man2/move_pages.2 | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/man2/move_pages.2 b/man2/move_pages.2
>> index 2d96468..2a2f3cd 100644
>> --- a/man2/move_pages.2
>> +++ b/man2/move_pages.2
>> @@ -192,9 +192,8 @@ was specified or an attempt was made to migrate 
>> pages of a kernel thread.
>>   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
>> +No pages were found.
>> +All pages are either not present, had an invalid address or could 
>> not be
>>   moved because they were mapped by multiple processes.
>>   .TP
>>   .B EPERM
>>
>
> 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.

>
>
> thanks,