From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id 1DDFD6B005C for ; Wed, 30 May 2012 15:20:14 -0400 (EDT) Received: by mail-pz0-f50.google.com with SMTP id h15so213502dan.23 for ; Wed, 30 May 2012 12:20:13 -0700 (PDT) From: Pravin B Shelar Subject: [Resend PATCH v2] mm: Fix slab->page _count corruption. Date: Wed, 30 May 2012 12:20:10 -0700 Message-Id: <1338405610-1788-1-git-send-email-pshelar@nicira.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, aarcange@redhat.com Cc: linux-mm@kvack.org, abhide@nicira.com, Pravin B Shelar On arches that do not support this_cpu_cmpxchg_double slab_lock is used to do atomic cmpxchg() on double word which contains page->_count. page count can be changed from get_page() or put_page() without taking slab_lock. That corrupts page counter. Following patch fixes it by moving page->_count out of cmpxchg_double data. So that slub does no change it while updating slub meta-data in struct page. Reported-by: Amey Bhide Signed-off-by: Pravin B Shelar Acked-by: Christoph Lameter --- include/linux/mm_types.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 18b48c4..e54a6b0 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -57,8 +57,16 @@ struct page { }; union { +#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \ + defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) /* Used for cmpxchg_double in slub */ unsigned long counters; +#else + /* Keep _count separate from slub cmpxchg_double data, + * As rest of double word is protected by slab_lock + * but _count is not. */ + unsigned counters; +#endif struct { -- 1.7.10 -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org