From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon_vma() Date: Fri, 9 Apr 2010 11:19:01 +0900 Message-ID: References: <20100408191737.296180458@chello.nl> <20100408192722.687144862@chello.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-pz0-f193.google.com ([209.85.222.193]:63134 "EHLO mail-pz0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751680Ab0DICTB (ORCPT ); Thu, 8 Apr 2010 22:19:01 -0400 In-Reply-To: <20100408192722.687144862@chello.nl> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: Andrea Arcangeli , Avi Kivity , Thomas Gleixner , Rik van Riel , Ingo Molnar , akpm@linux-foundation.org, Linus Torvalds , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Benjamin Herrenschmidt , David Miller , Hugh Dickins , Mel Gorman , Nick Piggin Hi, Peter. On Fri, Apr 9, 2010 at 4:17 AM, Peter Zijlstra wrote: > There is nothing preventing the anon_vma from being detached while we > are spinning to acquire the lock. Most (all?) current users end up > calling something like vma_address(page, vma) on it, which has a > fairly good chance of weeding out wonky vmas. > > However suppose the anon_vma got freed and re-used while we were > waiting to acquire the lock, and the new anon_vma fits with the > page->index (because that is the only thing vma_address() uses to > determine if the page fits in a particular vma, we could end up > traversing faulty anon_vma chains. We have second defense rule by page_check_address. Before anon_vma is detached, pte of pages on the anon_vma should be zeroed. So can't page_check_address close the race? Thanks for good trial for good feature. -- Kind regards, Minchan Kim