From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f51.google.com (mail-pb0-f51.google.com [209.85.160.51]) by kanga.kvack.org (Postfix) with ESMTP id 47E186B0031 for ; Tue, 4 Feb 2014 19:22:56 -0500 (EST) Received: by mail-pb0-f51.google.com with SMTP id un15so9096000pbc.24 for ; Tue, 04 Feb 2014 16:22:55 -0800 (PST) Received: from mail-pb0-x22f.google.com (mail-pb0-x22f.google.com [2607:f8b0:400e:c01::22f]) by mx.google.com with ESMTPS id l8si26621913pao.152.2014.02.04.16.22.55 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Feb 2014 16:22:55 -0800 (PST) Received: by mail-pb0-f47.google.com with SMTP id rp16so9123719pbb.6 for ; Tue, 04 Feb 2014 16:22:55 -0800 (PST) Date: Tue, 4 Feb 2014 16:22:53 -0800 (PST) From: David Rientjes Subject: [patch v2] mm, page_alloc: make first_page visible before PageTail In-Reply-To: Message-ID: References: <20140203122052.GC2495@dhcp22.suse.cz> <20140203162036.GJ2495@dhcp22.suse.cz> <52EFC93D.3030106@suse.cz> <20140204160641.8f5d369eeb2d0318618d6d5f@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Holger Kiehl Cc: Christoph Lameter , Rafael Aquini , Vlastimil Babka , Michal Hocko , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned pages") introduces page_count(page) into memory compaction which dereferences page->first_page if PageTail(page). Introduce a store memory barrier to ensure page->first_page is properly initialized so that code that does page_count(page) on pages off the lru always have a valid p->first_page. Reported-by: Holger Kiehl Signed-off-by: David Rientjes --- v2: with commentary, per checkpatch mm/page_alloc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -369,9 +369,11 @@ void prep_compound_page(struct page *page, unsigned long order) __SetPageHead(page); for (i = 1; i < nr_pages; i++) { struct page *p = page + i; - __SetPageTail(p); set_page_count(p, 0); p->first_page = page; + /* Make sure p->first_page is always valid for PageTail() */ + smp_wmb(); + __SetPageTail(p); } } -- 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