linux-kernel - Re: [PATCH 3/3] mm: fix return value in __alloc_contig_migrate

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Message-ID: <op.whldt4a73l0zgt@mpn-glaptop>
Date:	Tue, 17 Jul 2012 15:16:42 +0200
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	"JoonSoo Kim" <js1304@...il.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, "Marek Szyprowski" <m.szyprowski@...sung.com>,
	"Minchan Kim" <minchan@...nel.org>,
	"Christoph Lameter" <cl@...ux.com>
Subject: Re: [PATCH 3/3] mm: fix return value in
 __alloc_contig_migrate_range()

On Mon, 16 Jul 2012 20:40:56 +0200, JoonSoo Kim <js1304@...il.com> wrote:

> 2012/7/17 Michal Nazarewicz <mina86@...a86.com>:
>> Joonsoo Kim <js1304@...il.com> writes:
>>
>>> migrate_pages() would return positive value in some failure case,
>>> so 'ret > 0 ? 0 : ret' may be wrong.
>>> This fix it and remove one dead statement.
>>>
>>> Signed-off-by: Joonsoo Kim <js1304@...il.com>
>>> Cc: Michal Nazarewicz <mina86@...a86.com>
>>> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
>>> Cc: Minchan Kim <minchan@...nel.org>
>>> Cc: Christoph Lameter <cl@...ux.com>
>>
>> Have you actually encountered this problem?  If migrate_pages() fails
>> with a positive value, the code that you are removing kicks in and
>> -EBUSY is assigned to ret (now that I look at it, I think that in the
>> current code the "return ret > 0 ? 0 : ret;" statement could be reduced
>> to "return ret;").  Your code seems to be cleaner, but the commit
>> message does not look accurate to me.
>>
>
> I don't encounter this problem yet.
>
> If migrate_pages() with offlining false meets KSM page, then migration failed.
> In this case, failed page is removed from cc.migratepage list and
> return failed count.

Good point.

-- 
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.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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