From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by kanga.kvack.org (Postfix) with ESMTP id 9B3ED6B0032 for ; Tue, 9 Dec 2014 02:41:38 -0500 (EST) Received: by mail-pa0-f52.google.com with SMTP id eu11so37912pac.25 for ; Mon, 08 Dec 2014 23:41:38 -0800 (PST) Received: from mailout4.samsung.com (mailout4.samsung.com. [203.254.224.34]) by mx.google.com with ESMTPS id l3si452996pdl.205.2014.12.08.23.41.36 for (version=TLSv1 cipher=RC4-MD5 bits=128/128); Mon, 08 Dec 2014 23:41:36 -0800 (PST) Received: from epcpsbgm2.samsung.com (epcpsbgm2 [203.254.230.27]) by mailout4.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0NGB00JIU1DAFV10@mailout4.samsung.com> for linux-mm@kvack.org; Tue, 09 Dec 2014 16:41:34 +0900 (KST) From: Weijie Yang Subject: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check Date: Tue, 09 Dec 2014 15:40:35 +0800 Message-id: <000001d01383$8e0f1120$aa2d3360$%yang@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit Content-language: zh-cn Sender: owner-linux-mm@kvack.org List-ID: To: mgorman@suse.de Cc: 'Andrew Morton' , 'Johannes Weiner' , 'Rik van Riel' , linux-mm@kvack.org, linux-kernel@vger.kernel.org, 'Weijie Yang' If the free page and its buddy has different zone id, the current zone->lock cann't prevent buddy page getting allocated, this could trigger VM_BUG_ON_PAGE in a very tiny chance: cpu 0: cpu 1: hold zone_1 lock check page and it buddy PageBuddy(buddy) is true hold zone_2 lock page_order(buddy) == order is true alloc buddy trigger VM_BUG_ON_PAGE(page_count(buddy) != 0) This patch fixes this issue by placing the zone id check before the VM_BUG_ON_PAGE check. Signed-off-by: Weijie Yang --- mm/page_alloc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 616a2c9..491d055 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -488,17 +488,15 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, return 0; if (page_is_guard(buddy) && page_order(buddy) == order) { - VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); - if (page_zone_id(page) != page_zone_id(buddy)) return 0; + VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); + return 1; } if (PageBuddy(buddy) && page_order(buddy) == order) { - VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); - /* * zone check is done late to avoid uselessly * calculating zone/node ids for pages that could @@ -507,6 +505,8 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, if (page_zone_id(page) != page_zone_id(buddy)) return 0; + VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); + return 1; } return 0; -- 1.7.10.4 -- 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