From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030455AbWGZIxL (ORCPT ); Wed, 26 Jul 2006 04:53:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030456AbWGZIxK (ORCPT ); Wed, 26 Jul 2006 04:53:10 -0400 Received: from mtagate1.uk.ibm.com ([195.212.29.134]:30442 "EHLO mtagate1.uk.ibm.com") by vger.kernel.org with ESMTP id S1030455AbWGZIxJ (ORCPT ); Wed, 26 Jul 2006 04:53:09 -0400 Date: Wed, 26 Jul 2006 10:50:28 +0200 From: Heiko Carstens To: Christoph Lameter Cc: Andrew Morton , linux-kernel@vger.kernel.org, Pekka Enberg , linux-mm@kvack.org, Martin Schwidefsky Subject: [patch 1/2] slab: always consider caller mandated alignment Message-ID: <20060726085028.GC9592@osiris.boeblingen.de.ibm.com> References: <20060722110601.GA9572@osiris.boeblingen.de.ibm.com> <20060722162607.GA10550@osiris.ibm.com> <20060723073500.GA10556@osiris.ibm.com> <20060723162427.GA10553@osiris.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060723162427.GA10553@osiris.ibm.com> User-Agent: mutt-ng/devel-r804 (Linux) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Heiko Carstens In case of CONFIG_DEBUG_SLAB kmem_cache_create() creates caches with an alignment lesser than ARCH_KMALLOC_MINALIGN. This breaks s390 (32bit), since it needs an eight byte alignment. Also it doesn't behave like it's decribed in mm/slab.c : * Enforce a minimum alignment for the kmalloc caches. * Usually, the kmalloc caches are cache_line_size() aligned, except when * DEBUG and FORCED_DEBUG are enabled, then they are BYTES_PER_WORD aligned. * Some archs want to perform DMA into kmalloc caches and need a guaranteed * alignment larger than BYTES_PER_WORD. ARCH_KMALLOC_MINALIGN allows that. * Note that this flag disables some debug features. For example the following might happen if kmem_cache_create() gets called with -- size: 64; align: 8; flags with SLAB_HWCACHE_ALIGN, SLAB_RED_ZONE and SLAB_STORE_USER set. These are the steps as numbered in kmem_cache_create() where 5) is after the "if (flags & SLAB_RED_ZONE)" statement. 1) align: 8 ralign 64 2) align: 8 ralign 64 3) align: 8 ralign 64 4) align: 64 ralign 64 5) align: 4 ralign 64 Note that in this case in step 3) the flags SLAB_RED_ZONE and SLAB_STORE_USER don't get masked out and that this causes an BYTES_PER_WORD alignment in step 5) which breaks s390. Cc: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Heiko Carstens --- mm/slab.c | 3 +++ 1 files changed, 3 insertions(+) Index: linux-2.6/mm/slab.c =================================================================== --- linux-2.6.orig/mm/slab.c 2006-07-24 09:41:36.000000000 +0200 +++ linux-2.6/mm/slab.c 2006-07-26 09:55:54.000000000 +0200 @@ -2109,6 +2109,9 @@ if (ralign > BYTES_PER_WORD) flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); } + if (align > BYTES_PER_WORD) + flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); + /* * 4) Store it. Note that the debug code below can reduce * the alignment to BYTES_PER_WORD.