From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933865Ab1DNSXM (ORCPT ); Thu, 14 Apr 2011 14:23:12 -0400 Received: from mail.windriver.com ([147.11.1.11]:38261 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933071Ab1DNRqi (ORCPT ); Thu, 14 Apr 2011 13:46:38 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, KAMEZAWA Hiroyuki , Andrew Morton , Linus Torvalds , Paul Gortmaker Subject: [34-longterm 038/209] mm: fix is_mem_section_removable() page_order BUG_ON check Date: Thu, 14 Apr 2011 13:41:08 -0400 Message-Id: <1302803039-9400-39-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1302803039-9400-1-git-send-email-paul.gortmaker@windriver.com> References: <1302803039-9400-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: KAMEZAWA Hiroyuki ===================================================================== | This is a commit scheduled for the next v2.6.34 longterm release. | | If you see a problem with using this for longterm, please comment.| ===================================================================== commit 572438f9b52236bd8938b1647cc15e027d27ef55 upstream. page_order() is called by memory hotplug's user interface to check the section is removable or not. (is_mem_section_removable()) It calls page_order() withoug holding zone->lock. So, even if the caller does if (PageBuddy(page)) ret = page_order(page) ... The caller may hit BUG_ON(). For fixing this, there are 2 choices. 1. add zone->lock. 2. remove BUG_ON(). is_mem_section_removable() is used for some "advice" and doesn't need to be 100% accurate. This is_removable() can be called via user program.. We don't want to take this important lock for long by user's request. So, this patch removes BUG_ON(). Signed-off-by: KAMEZAWA Hiroyuki Acked-by: Wu Fengguang Acked-by: Michal Hocko Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Paul Gortmaker --- mm/internal.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 6a697bb..dedb0af 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -62,7 +62,7 @@ extern bool is_free_buddy_page(struct page *page); */ static inline unsigned long page_order(struct page *page) { - VM_BUG_ON(!PageBuddy(page)); + /* PageBuddy() must be checked by the caller */ return page_private(page); } -- 1.7.4.4