linux-kernel - Re: [RESEND PATCH 4/4 v3] mm: fix possible incorrect return value of move

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Message-ID: <CAAmzW4MdiJOaZW_b+fz1uYyj0asTCveN=24st4xKymKEvkzdgQ@mail.gmail.com>
Date:	Sat, 28 Jul 2012 15:09:05 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Brice Goglin <brice@...i.com>,
	Minchan Kim <minchan@...nel.org>
Subject: Re: [RESEND PATCH 4/4 v3] mm: fix possible incorrect return value of
 move_pages() syscall

2012/7/28 Christoph Lameter <cl@...ux.com>:
> On Sat, 28 Jul 2012, Joonsoo Kim wrote:
>
>> move_pages() syscall may return success in case that
>> do_move_page_to_node_array return positive value which means migration failed.
>
> Nope. It only means that the migration for some pages has failed. This may
> still be considered successful for the app if it moves 10000 pages and one
> failed.
>
> This patch would break the move_pages() syscall because an error code
> return from do_move_pages_to_node_array() will cause the status byte for
> each page move to not be updated anymore. Application will not be able to
> tell anymore which pages were successfully moved and which are not.

In case of returning non-zero, valid status is not required according
to man page.
So, this patch would not break the move_pages() syscall.
But, I agree that returning positive value only means that the
migration for some pages has failed.
This is my mistake, so please drop this patch.
Thanks for review.
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