From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id A7F2E6B01E3 for ; Thu, 22 Apr 2010 06:35:06 -0400 (EDT) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o3MAZ4K7017176 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 22 Apr 2010 19:35:04 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id 0EF0045DE57 for ; Thu, 22 Apr 2010 19:35:04 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id DF95845DE51 for ; Thu, 22 Apr 2010 19:35:03 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id C024D1DB8015 for ; Thu, 22 Apr 2010 19:35:03 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 6D7381DB8016 for ; Thu, 22 Apr 2010 19:35:03 +0900 (JST) Date: Thu, 22 Apr 2010 19:31:06 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages Message-Id: <20100422193106.9ffad4ec.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <1271797276-31358-1-git-send-email-mel@csn.ul.ie> <20100421150037.GJ30306@csn.ul.ie> <20100421151417.GK30306@csn.ul.ie> <20100421153421.GM30306@csn.ul.ie> <20100422092819.GR30306@csn.ul.ie> <20100422184621.0aaaeb5f.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Mel Gorman , Christoph Lameter , Andrew Morton , Andrea Arcangeli , Adam Litke , Avi Kivity , David Rientjes , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Thu, 22 Apr 2010 19:13:12 +0900 Minchan Kim wrote: > On Thu, Apr 22, 2010 at 6:46 PM, KAMEZAWA Hiroyuki > wrote: > > Hmm..in my test, the case was. > > > > Before try_to_unmap: > > A A A A mapcount=1, SwapCache, remap_swapcache=1 > > After remap > > A A A A mapcount=0, SwapCache, rc=0. > > > > So, I think there may be some race in rmap_walk() and vma handling or > > anon_vma handling. migration_entry isn't found by rmap_walk. > > > > Hmm..it seems this kind patch will be required for debug. > > I looked do_swap_page, again. > lock_page is called long after migration_entry_wait. > It means lock_page can't close the race. > > So I think this BUG is possible. > What do you think? > I think it's not a problem. When migration-entry-wait is called, enry_wait() does pte_lock(); check migration_pte check it's locked. And after wait_on_page_locked(), it just returns to user and cause page fault again. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org