linux-kernel - Re: [v2 PATCH] mm: move_pages: report the number of non-attempted pages

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Message-ID: <20200123224035.GA29851@richard>
Date:   Fri, 24 Jan 2020 06:40:35 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>, mhocko@...e.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [v2 PATCH] mm: move_pages: report the number of non-attempted
 pages

On Wed, Jan 22, 2020 at 07:56:50PM -0800, Yang Shi wrote:
>
>
>On 1/22/20 7:27 PM, Wei Yang wrote:
>> On Thu, Jan 23, 2020 at 07:38:51AM +0800, Yang Shi wrote:
>> > Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"),
>> > the semantic of move_pages() was changed to return the number of
>> > non-migrated pages (failed to migration) and the call would be aborted
>> > immediately if migrate_pages() returns positive value.  But it didn't
>> > report the number of pages that we even haven't attempted to migrate.
>> > So, fix it by including non-attempted pages in the return value.
>> > 
>> First, we want to change the semantic of move_pages(2). The return value
>> indicates the number of pages we didn't managed to migrate?
>
>This is my understanding.
>
>> 
>> Second, the return value from migrate_pages() doesn't mean the number of pages
>> we failed to migrate. For example, one -ENOMEM is returned on the first page,
>> migrate_pages() would return 1. But actually, no page successfully migrated.
>
>This would not happen at all since migrate_pages() would just return -ENOMEM
>instead of a positive value, right?
>

Oh, you are right.


-- 
Wei Yang
Help you, Help me