linux-kernel - Re: [BUGFIX][PATCH] fix wrong lru rotate back at lumpty reclaim

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Message-Id: <20090609181745.DD88.A69D9226@jp.fujitsu.com>
Date:	Tue,  9 Jun 2009 18:29:29 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	riel@...hat.com
Subject: Re: [BUGFIX][PATCH] fix wrong lru rotate back at lumpty reclaim

> 
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> In lumpty reclaim, "cursor_page" is found just by pfn. Then, we don't know
     ^^^^^^
     lumpy?

> from which LRU "cursor" page came from. Then, putback it to "src" list is BUG.
> Just leave it as it is.
> (And I think rotate here is overkilling even if "src" is correct.)
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Yes, thanks great catch!

lumpy reclaimed neighbor pages doesn't need to ratate, it because
neighbor pages doesn't stay in head of lru list.


   Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>



> ---
>  mm/vmscan.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> Index: mmotm-2.6.30-Jun4/mm/vmscan.c
> ===================================================================
> --- mmotm-2.6.30-Jun4.orig/mm/vmscan.c
> +++ mmotm-2.6.30-Jun4/mm/vmscan.c
> @@ -940,10 +940,9 @@ static unsigned long isolate_lru_pages(u
>  				nr_taken++;
>  				scan++;
>  				break;
> -
>  			case -EBUSY:
> -				/* else it is being freed elsewhere */
> -				list_move(&cursor_page->lru, src);
> +				/* Do nothing because we don't know where
> + 				   cusrsor_page comes from */
>  			default:
>  				break;	/* ! on LRU or wrong list */
>  			}
> 
> --
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