Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170Ab0DMHFG (ORCPT ); Tue, 13 Apr 2010 03:05:06 -0400 Received: from exprod5og102.obsmtp.com ([64.18.0.143]:52419 "EHLO exprod5og102.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751916Ab0DMHFE convert rfc822-to-8bit (ORCPT ); Tue, 13 Apr 2010 03:05:04 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Tue, 13 Apr 2010 15:05:00 +0800 Message-ID: Subject: Re: [PATCH - V2] Fix missing of last user while dumping slab corruption log From: TAO HU To: Pekka Enberg Cc: linux-kernel@vger.kernel.org, cl@linux-foundation.org, mpm@selenic.com, linux-mm@kvack.org, dwmw2@infradead.org, TAO HU , ShiYong LI Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3240 Lines: 95 Hi, Pekka Enberg Actually we greped "kmem_cache_create" in whole kernel souce tree (2.6.29 and 2.6.32). Either "align" equal to "0" or flag SLAB_HWCACHE_ALIGN is used when calling kmem_cache_create(). Seems all of arch's cache-line-size is multiple of 64-bit/8-byte (sizeof(long long)) except arch-microblaze (4-byte). The smallest (except arch-microblaze) cache-line-size is 2^4= 16-byte as I can see. So even considering possible sizeof(long long) == 128-bit/16-byte, it is still safe to apply Shiyong's original version. Anyway, Shiyong's new patch check the weired situation that "align > sizeof(long long) && align is NOT multiple of sizeof (long long)" Let us know whether the new version address your concerns. -- Best Regards Hu Tao On Mon, Apr 12, 2010 at 1:50 PM, ShiYong LI wrote: > Hi, > > Compared to previous version, add alignment checking to make sure > memory space storing redzone2 and last user tags is 8 byte alignment. > > From 949e8c29e8681a2359e23a8fbd8b9d4833f42344 Mon Sep 17 00:00:00 2001 > From: Shiyong Li > Date: Mon, 12 Apr 2010 13:48:21 +0800 > Subject: [PATCH] Fix missing of last user info while getting > DEBUG_SLAB config enabled. > > Even with SLAB_RED_ZONE and SLAB_STORE_USER enabled, kernel would NOT > store redzone and last user data around allocated memory space if arch > cache line > sizeof(unsigned long long). As a result, last user information > is unexpectedly MISSED while dumping slab corruption log. > > This fix makes sure that redzone and last user tags get stored unless > the required alignment breaks redzone's. > > Signed-off-by: Shiyong Li > --- > ?mm/slab.c | ? ?8 ++++---- > ?1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index a8a38ca..b97c57e 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -2267,8 +2267,8 @@ kmem_cache_create (const char *name, size_t > size, size_t align, > ? ? ? ?if (ralign < align) { > ? ? ? ? ? ? ? ?ralign = align; > ? ? ? ?} > - ? ? ? /* disable debug if necessary */ > - ? ? ? if (ralign > __alignof__(unsigned long long)) > + ? ? ? /* disable debug if not aligning with REDZONE_ALIGN */ > + ? ? ? if (ralign & (__alignof__(unsigned long long) - 1)) > ? ? ? ? ? ? ? ?flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); > ? ? ? ?/* > ? ? ? ? * 4) Store it. > @@ -2289,8 +2289,8 @@ kmem_cache_create (const char *name, size_t > size, size_t align, > ? ? ? ? */ > ? ? ? ?if (flags & SLAB_RED_ZONE) { > ? ? ? ? ? ? ? ?/* add space for red zone words */ > - ? ? ? ? ? ? ? cachep->obj_offset += sizeof(unsigned long long); > - ? ? ? ? ? ? ? size += 2 * sizeof(unsigned long long); > + ? ? ? ? ? ? ? cachep->obj_offset += align; > + ? ? ? ? ? ? ? size += align + sizeof(unsigned long long); > ? ? ? ?} > ? ? ? ?if (flags & SLAB_STORE_USER) { > ? ? ? ? ? ? ? ?/* user store requires one word storage behind the end of > -- > 1.6.0.4 > > > > > > -- > Thanks & Best Regards > Shiyong > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/