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

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Message-ID: <28c262360906090300s13f4ee09mcc9622c1e477eaad@mail.gmail.com>
Date:	Tue, 9 Jun 2009 19:00:20 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"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

On Tue, Jun 9, 2009 at 6:15 PM, KAMEZAWA
Hiroyuki<kamezawa.hiroyu@...fujitsu.com> wrote:
>
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> In lumpty reclaim, "cursor_page" is found just by pfn. Then, we don't know
> 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>
> ---
>  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:

We can remove case -EBUSY itself, too.
It is meaningless.

> -                               /* 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 */

Hmm.. what meaning of this break ?
We are in switch case.
This "break" can't go out of loop.
But comment said "abort this block scan".

If I understand it properly , don't we add goto phrase ?

>                        }
>
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-- 
Kinds regards,
Minchan Kim