linux-kernel - Re: [PATCH 3/7] vmscan: synchrounous lumpy reclaim use lock_page() instead trylock

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Message-ID: <AANLkTimYxERF5Gj300tKyF-DANQ4dae-wHpadf2putyh@mail.gmail.com>
Date:	Fri, 6 Aug 2010 09:52:37 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mel@....ul.ie>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 3/7] vmscan: synchrounous lumpy reclaim use lock_page() 
	instead trylock_page()

On Thu, Aug 5, 2010 at 11:17 PM, Minchan Kim <minchan.kim@...il.com> wrote:
> On Thu, Aug 05, 2010 at 03:13:39PM +0900, KOSAKI Motohiro wrote:
>> When synchrounous lumpy reclaim, there is no reason to give up to
>> reclaim pages even if page is locked. We use lock_page() instead
>> trylock_page() in this case.
>>
>> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> ---
>>  mm/vmscan.c |    4 +++-
>>  1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 1cdc3db..833b6ad 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -665,7 +665,9 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>               page = lru_to_page(page_list);
>>               list_del(&page->lru);
>>
>> -             if (!trylock_page(page))
>> +             if (sync_writeback == PAGEOUT_IO_SYNC)
>> +                     lock_page(page);
>> +             else if (!trylock_page(page))
>>                       goto keep;
>>
>>               VM_BUG_ON(PageActive(page));
>> --
>> 1.6.5.2
>>
>>
>>
>
> Hmm. We can make sure lumpy already doesn't select the page locked?
> I mean below scenario.
>
> LRU head -> page A -> page B -> LRU tail
>
> lock_page(page A)
> some_function()
> direct reclaim
> select victim page B
> enter lumpy mode
> select victim page A as well as page B
> shrink_page_list
> lock_page(page A)
>
>
> --
> Kind regards,
> Minchan Kim
>

Ignore above comment.
lock_page doesn't have a deadlock problem. My bad.

Reviewed-by: Minchan Kim <minchan.kim@...il.com>



-- 
Kind regards,
Minchan Kim
--
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