From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx135.postini.com [74.125.245.135]) by kanga.kvack.org (Postfix) with SMTP id D4D866B004D for ; Mon, 14 May 2012 18:30:02 -0400 (EDT) Received: by mail-gg0-f178.google.com with SMTP id q6so4554827ggc.37 for ; Mon, 14 May 2012 15:30:01 -0700 (PDT) From: Pravin B Shelar Subject: [PATCH v2] mm: Fix slab->page _count corruption. Date: Mon, 14 May 2012 15:29:57 -0700 Message-Id: <1337034597-1826-1-git-send-email-pshelar@nicira.com> Sender: owner-linux-mm@kvack.org List-ID: To: cl@linux.com, penberg@kernel.org, mpm@selenic.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, jesse@nicira.com, 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 --- 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 dad95bd..5f558dc 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