From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753389AbaHTXd2 (ORCPT ); Wed, 20 Aug 2014 19:33:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45325 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752988AbaHTXd1 (ORCPT ); Wed, 20 Aug 2014 19:33:27 -0400 Date: Wed, 20 Aug 2014 20:33:09 -0300 From: Rafael Aquini To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, Andrew Morton , Sasha Levin , Andrey Ryabinin , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/7] mm/balloon_compaction: keep ballooned pages away from normal migration path Message-ID: <20140820233308.GC3457@optiplex.redhat.com> References: <20140820150435.4194.28003.stgit@buzz> <20140820150440.4194.70267.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140820150440.4194.70267.stgit@buzz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 20, 2014 at 07:04:40PM +0400, Konstantin Khlebnikov wrote: > Proper testing shows yet another problem in balloon migration: it works only > once for each page. balloon_page_movable() check page flags and page_count. > In __unmap_and_move page is locked, reference counter is elevated, so > balloon_page_movable() _always_ fails here. As result in __unmap_and_move() > migration goes to the normal migration path. > > Balloon ->migratepage() is so special, it returns MIGRATEPAGE_BALLOON_SUCCESS > instead of MIGRATEPAGE_SUCCESS. After that in move_to_new_page() successfully > migrated page got NULL into its mapping pointer and loses connectivity with > balloon and ability for further migration. > > It's safe to use __is_movable_balloon_page here: page is isolated and pinned. > > Signed-off-by: Konstantin Khlebnikov > Cc: stable # v3.8 > --- > mm/migrate.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index f78ec9b..161d044 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -873,7 +873,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, > } > } > > - if (unlikely(balloon_page_movable(page))) { > + if (unlikely(__is_movable_balloon_page(page))) { > /* > * A ballooned page does not need any special attention from > * physical to virtual reverse mapping procedures. > Acked-by: Rafael Aquini