linux-kernel - Re: [PATCH] mm: vmscan: fix typo in isolating lru pages

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Message-ID: <CAJd=RBAp-nC2-VoxgfZ2NjDz08hVkjD_YOoRWuO54ASQCL5hvA@mail.gmail.com>
Date:	Sat, 31 Dec 2011 22:25:29 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH] mm: vmscan: fix typo in isolating lru pages

On Fri, Dec 30, 2011 at 7:07 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 29 Dec 2011 20:38:41 +0800
> Hillf Danton <dhillf@...il.com> wrote:
>
>> It is not the tag page but the cursor page that we should process, and it looks
>> a typo.
>>
>> Signed-off-by: Hillf Danton <dhillf@...il.com>
>> Cc: Michal Hocko <mhocko@...e.cz>
>> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: David Rientjes <rientjes@...gle.com>
>> Cc: Hugh Dickins <hughd@...gle.com>
>> ---
>>
>> --- a/mm/vmscan.c     Thu Dec 29 20:20:16 2011
>> +++ b/mm/vmscan.c     Thu Dec 29 20:23:30 2011
>> @@ -1231,13 +1231,13 @@ static unsigned long isolate_lru_pages(u
>>
>>                               mem_cgroup_lru_del(cursor_page);
>>                               list_move(&cursor_page->lru, dst);
>> -                             isolated_pages = hpage_nr_pages(page);
>> +                             isolated_pages = hpage_nr_pages(cursor_page);
>>                               nr_taken += isolated_pages;
>>                               nr_lumpy_taken += isolated_pages;
>>                               if (PageDirty(cursor_page))
>>                                       nr_lumpy_dirty += isolated_pages;
>>                               scan++;
>> -                             pfn += isolated_pages-1;
>> +                             pfn += isolated_pages - 1;
>>                       } else {
>>                               /*
>>                                * Check if the page is freed already.
>
> This problem looks pretty benign in mainline.  But Andrea's "mm:
> vmscan: check if we isolated a compound page during lumpy scan" came
> along and uses isolated_pages rather a lot more, including using it to
> advance across the pfn array.
>
> I jiggled your patch to suit current mainline then reworked everything
> else so we end up with this result.
>
Hi folks

Thanks for your comments, ack and nack, in 2011.

Happy New Year

Hillf Danton