Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756931Ab0DVALI (ORCPT ); Wed, 21 Apr 2010 20:11:08 -0400 Received: from mail-gw0-f46.google.com ([74.125.83.46]:33958 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754508Ab0DVALH convert rfc822-to-8bit (ORCPT ); Wed, 21 Apr 2010 20:11:07 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=fER5R6bAmujLsUpT/6wF42bYe8NPzmT8ey29MyaDhmCh4Rnow1uYI852zc9OspH81h A/hc8+uhe3GsBbBWTCBvrOE8mYI9dZbauCMiCZY1ytvyHabB+/T0kY7/e4fmvj8YVj/O aYpk3qXDqbIXTrNg8g6XaM/v/kF0x7gp6cCsQ= MIME-Version: 1.0 In-Reply-To: <20100422085943.3d908a4b.kamezawa.hiroyu@jp.fujitsu.com> References: <1271797276-31358-1-git-send-email-mel@csn.ul.ie> <1271797276-31358-5-git-send-email-mel@csn.ul.ie> <20100422085943.3d908a4b.kamezawa.hiroyu@jp.fujitsu.com> Date: Thu, 22 Apr 2010 09:11:04 +0900 Message-ID: Subject: Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages From: Minchan Kim To: KAMEZAWA Hiroyuki Cc: Christoph Lameter , Mel Gorman , Andrew Morton , Andrea Arcangeli , Adam Litke , Avi Kivity , David Rientjes , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1818 Lines: 54 On Thu, Apr 22, 2010 at 8:59 AM, KAMEZAWA Hiroyuki wrote: > On Wed, 21 Apr 2010 09:30:20 -0500 (CDT) > Christoph Lameter wrote: > >> On Tue, 20 Apr 2010, Mel Gorman wrote: >> >> > @@ -520,10 +521,12 @@ static int move_to_new_page(struct page *newpage, struct page *page) >> >     else >> >             rc = fallback_migrate_page(mapping, newpage, page); >> > >> > -   if (!rc) >> > -           remove_migration_ptes(page, newpage); >> > -   else >> > +   if (rc) { >> >             newpage->mapping = NULL; >> > +   } else { >> > +           if (remap_swapcache) >> > +                   remove_migration_ptes(page, newpage); >> > +   } >> >> You are going to keep the migration ptes after the page has been unlocked? >> Or is remap_swapcache true if its not a swapcache page? >> >> Maybe you meant >> >> if (!remap_swapcache) >> > > Ah....Can I confirm my understanding ? > > remap_swapcache == true only when >  The old page was ANON && it is not mapped. && it is SwapCache. > > We do above check under lock_page(). So, this SwapCache is never mapped until > we release lock_page() on the old page. So, we don't use migration_pte in > this case because try_to_unmap() do nothing and don't need to call > remove_migration_pte(). Yes. so I thought what kinds of race happened. Firstly I doubt fork and migration. but It isn't. I can't understand how this bug happens. Apparently, We have been missed something. I will look into this further. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/