From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 8DF036B01E3 for ; Wed, 7 Apr 2010 10:33:02 -0400 (EDT) Received: from il06vts03.mot.com (il06vts03.mot.com [129.188.137.143]) by mdgate1.mot.com (8.14.3/8.14.3) with SMTP id o37EXDtm001271 for ; Wed, 7 Apr 2010 08:33:13 -0600 (MDT) Received: from mail-iw0-f199.google.com (mail-iw0-f199.google.com [209.85.223.199]) by mdgate1.mot.com (8.14.3/8.14.3) with ESMTP id o37EEsN1024819 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=OK) for ; Wed, 7 Apr 2010 08:33:13 -0600 (MDT) Received: by mail-iw0-f199.google.com with SMTP id 37so307955iwn.15 for ; Wed, 07 Apr 2010 07:32:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: Date: Wed, 7 Apr 2010 22:32:55 +0800 Message-ID: Subject: Re: [PATCH] Fix missing of last user while dumping slab corruption log From: TAO HU Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Pekka Enberg Cc: linux-kernel@vger.kernel.org, cl@linux-foundation.org, mpm@selenic.com, linux-mm@kvack.org, ShiYong LI List-ID: Hi, Pekka Enberg Can we assume you have no objection for this patch? :) --=20 Best Regards Hu Tao On Tue, Apr 6, 2010 at 9:24 AM, TAO HU wrote: > Hi, Pekka Enberg > > This is the updated version with format fix and comments refinement. > Let us know whether you still have comments. > > -- > Best Regards > Hu Tao > > On Fri, Apr 2, 2010 at 3:21 PM, ShiYong LI wro= te: >> Hi, >> >> 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 informat= ion >> is unexpectedly MISSED while dumping slab corruption log. >> >> This patch makes sure that redzone and last user tags get stored whateve= r >> arch cache line. >> >> Compared to original codes, the change surely affects head redzone (redz= one1). >> Actually, with SLAB_RED_ZONE and SLAB_STORE_USER enabled, >> allocated memory layout is as below: >> >> [ redzone1 ] =A0 <--------- Affected area. >> [ real object space ] >> [ redzone2 ] >> [ last user ] >> [ ... ] >> >> Let's do some analysis: (whatever SLAB_STORE_USER is). >> >> 1) With SLAB_RED_ZONE on, "align" >=3D sizeof(unsigned long long) accord= ing to >> =A0 =A0the following codes: >> =A0 =A0 =A0 =A0/* 2) arch mandated alignment */ >> =A0 =A0 =A0 =A0if (ralign < ARCH_SLAB_MINALIGN) { >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ralign =3D ARCH_SLAB_MINALIGN; >> =A0 =A0 =A0 =A0} >> =A0 =A0 =A0 =A0/* 3) caller mandated alignment */ >> =A0 =A0 =A0 =A0if (ralign < align) { >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ralign =3D align; >> =A0 =A0 =A0 =A0} >> =A0 =A0 =A0 =A0... >> =A0 =A0 =A0 =A0/* >> =A0 =A0 =A0 =A0 * 4) Store it. >> =A0 =A0 =A0 =A0 */ >> =A0 =A0 =A0 =A0align =3D ralign; >> >> =A0 =A0That's to say, could guarantee that redzone1 does NOT get broken >> at all. Meanwhile, >> =A0 =A0Real object space could meet the need of cache line size by using >> "align" =A0argument. >> >> 2) With SLAB_RED_ZONE off, the change has no impact. >> >> >> From 03b28964311090533643acd267abe0cbc3c9b0a5 Mon Sep 17 00:00:00 2001 >> From: Shiyong Li >> Date: Fri, 2 Apr 2010 14:50:30 +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 informat= ion >> is unexpectedly MISSED while dumping slab corruption log. >> >> This fix makes sure that redzone and last user tags get stored whatever >> cache line. >> >> Signed-off-by: Shiyong Li >> --- >> =A0mm/slab.c | =A0 =A07 ++----- >> =A01 files changed, 2 insertions(+), 5 deletions(-) >> >> diff --git a/mm/slab.c b/mm/slab.c >> index a8a38ca..84af997 100644 >> --- a/mm/slab.c >> +++ b/mm/slab.c >> @@ -2267,9 +2267,6 @@ kmem_cache_create (const char *name, size_t >> size, size_t align, >> =A0 =A0 =A0 =A0if (ralign < align) { >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ralign =3D align; >> =A0 =A0 =A0 =A0} >> - =A0 =A0 =A0 /* disable debug if necessary */ >> - =A0 =A0 =A0 if (ralign > __alignof__(unsigned long long)) >> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 flags &=3D ~(SLAB_RED_ZONE | SLAB_STORE_US= ER); >> =A0 =A0 =A0 =A0/* >> =A0 =A0 =A0 =A0 * 4) Store it. >> =A0 =A0 =A0 =A0 */ >> @@ -2289,8 +2286,8 @@ kmem_cache_create (const char *name, size_t >> size, size_t align, >> =A0 =A0 =A0 =A0 */ >> =A0 =A0 =A0 =A0if (flags & SLAB_RED_ZONE) { >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* add space for red zone words */ >> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 cachep->obj_offset +=3D sizeof(unsigned lo= ng long); >> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 size +=3D 2 * sizeof(unsigned long long); >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 cachep->obj_offset +=3D align; >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 size +=3D align + sizeof(unsigned long lon= g); >> =A0 =A0 =A0 =A0} >> =A0 =A0 =A0 =A0if (flags & SLAB_STORE_USER) { >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* user store requires one word storage b= ehind the end of >> -- >> 1.6.0.4 >> >> >> Thanks & Best Regards >> Shiyong >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. =A0For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: email@kvack.org >> > -- 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