From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx116.postini.com [74.125.245.116]) by kanga.kvack.org (Postfix) with SMTP id CABA16B0083 for ; Mon, 14 May 2012 20:13:18 -0400 (EDT) Received: by mail-vb0-f50.google.com with SMTP id l1so4275673vba.9 for ; Mon, 14 May 2012 17:13:18 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1337034892.8512.652.camel@edumazet-glaptop> References: <1337034597-1826-1-git-send-email-pshelar@nicira.com> <1337034892.8512.652.camel@edumazet-glaptop> Date: Mon, 14 May 2012 17:13:17 -0700 Message-ID: Subject: Re: [PATCH v2] mm: Fix slab->page _count corruption. From: Pravin Shelar Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Eric Dumazet Cc: cl@linux.com, penberg@kernel.org, mpm@selenic.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jesse@nicira.com, abhide@nicira.com On Mon, May 14, 2012 at 3:34 PM, Eric Dumazet wrote: > On Mon, 2012-05-14 at 15:29 -0700, Pravin B Shelar wrote: >> 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. > > I say again : Page is owned by slub, so get_page() or put_page() is not > allowed ? > This is already done in multiple subsystem in Linux kernel. e.g. ocfs, xfs, etc. So object from slab can be passed to IO using DMA. I don't think this rule you referring to is enforced anywhere. Thanks, Pravin. -- 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