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

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Message-ID: <e8f208a7c6bec1818947c24658dc1561.squirrel@webmail-b.css.fujitsu.com>
Date:	Tue, 9 Jun 2009 20:20:29 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	"Minchan Kim" <minchan.kim@...il.com>
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"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


Minchan Kim wrote:
> 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.
>
Sure, will post v2 and remove EBUSY case.
(I'm sorry my webmail system converts a space to a multibyte char...
 then I cut some.)

>> - /* 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.
yes.

> But comment said "abort this block scan".
>
Where ? the comment says the cursor_page is not on lru (PG_lru is unset)
> If I understand it properly , don't we add goto phrase ?
>
No.

Just try next page on list.

Thank you for review, I'll post updated one tomorrow.
-Kame

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