From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756377AbZEVIDQ (ORCPT ); Fri, 22 May 2009 04:03:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753618AbZEVICx (ORCPT ); Fri, 22 May 2009 04:02:53 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:48506 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752792AbZEVICw (ORCPT ); Fri, 22 May 2009 04:02:52 -0400 Subject: Re: [PATCH] slab: fix generic PAGE_POISONING conflict with SLAB_RED_ZONE From: Pekka Enberg To: Ron Cc: cl@linux-foundation.org, mpm@selenic.com, linux-mm@kvack.org, akinobu.mita@gmail.com, linux-kernel@vger.kernel.org In-Reply-To: <20090521192822.GB4448@homer.shelbyville.oz> References: <20090521192822.GB4448@homer.shelbyville.oz> Date: Fri, 22 May 2009 11:02:52 +0300 Message-Id: <1242979372.13681.1.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Mailer: Evolution 2.24.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-05-22 at 04:58 +0930, Ron wrote: > A generic page poisoning mechanism was added with commit: > 6a11f75b6a17b5d9ac5025f8d048382fd1f47377 > which destructively poisons full pages with a bitpattern. > > On arches where PAGE_POISONING is used, this conflicts with the slab > redzone checking enabled by DEBUG_SLAB, scribbling bits all over its > magic words and making it complain about that quite emphatically. > > On x86 (and I presume at present all the other arches which set > ARCH_SUPPORTS_DEBUG_PAGEALLOC too), the kernel_map_pages() operation > is non destructive so it can coexist with the other DEBUG_SLAB > mechanisms just fine. > > This patch favours the expensive full page destruction test for > cases where there is a collision and it is explicitly selected. > > Signed-off-by: Ron Lee Applied, thanks! Pekka