From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f171.google.com (mail-wi0-f171.google.com [209.85.212.171]) by kanga.kvack.org (Postfix) with ESMTP id 16A046B0037 for ; Fri, 18 Jul 2014 02:54:47 -0400 (EDT) Received: by mail-wi0-f171.google.com with SMTP id hi2so303872wib.10 for ; Thu, 17 Jul 2014 23:54:47 -0700 (PDT) Received: from mail-wg0-x22d.google.com (mail-wg0-x22d.google.com [2a00:1450:400c:c00::22d]) by mx.google.com with ESMTPS id o2si9022684wje.108.2014.07.17.23.54.46 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 17 Jul 2014 23:54:46 -0700 (PDT) Received: by mail-wg0-f45.google.com with SMTP id x12so3100413wgg.16 for ; Thu, 17 Jul 2014 23:54:46 -0700 (PDT) Date: Fri, 18 Jul 2014 08:54:44 +0200 From: Michal Hocko Subject: Re: [patch] mm, writeback: prevent race when calculating dirty limits Message-ID: <20140718065444.GA21453@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Andrew Morton , Johannes Weiner , Rik van Riel , stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed 16-07-14 17:36:49, David Rientjes wrote: > Setting vm_dirty_bytes and dirty_background_bytes is not protected by any > serialization. > > Therefore, it's possible for either variable to change value after the > test in global_dirty_limits() to determine whether available_memory needs > to be initialized or not. > > Always ensure that available_memory is properly initialized. > > Cc: stable@vger.kernel.org > Signed-off-by: David Rientjes Makes sense to me Acked-by: Michal Hocko > --- > mm/page-writeback.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -261,14 +261,11 @@ static unsigned long global_dirtyable_memory(void) > */ > void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) > { > + const unsigned long available_memory = global_dirtyable_memory(); > unsigned long background; > unsigned long dirty; > - unsigned long uninitialized_var(available_memory); > struct task_struct *tsk; > > - if (!vm_dirty_bytes || !dirty_background_bytes) > - available_memory = global_dirtyable_memory(); > - > if (vm_dirty_bytes) > dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); > else -- Michal Hocko SUSE Labs -- 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