Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762441AbYA3Ond (ORCPT ); Wed, 30 Jan 2008 09:43:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757940AbYA3OnL (ORCPT ); Wed, 30 Jan 2008 09:43:11 -0500 Received: from relay1.sgi.com ([192.48.171.29]:51207 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757545AbYA3OnJ (ORCPT ); Wed, 30 Jan 2008 09:43:09 -0500 Date: Wed, 30 Jan 2008 08:43:06 -0600 From: Jack Steiner To: Andrea Arcangeli Cc: Christoph Lameter , Robin Holt , Avi Kivity , Izik Eidus , Nick Piggin , kvm-devel@lists.sourceforge.net, Benjamin Herrenschmidt , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com, Hugh Dickins Subject: Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Message-ID: <20080130144305.GA25193@sgi.com> References: <20080129162004.GL7233@v2.random> <20080129211759.GV7233@v2.random> <20080129220212.GX7233@v2.random> <20080130000039.GA7233@v2.random> <20080130002804.GA13840@sgi.com> <20080130133720.GM7233@v2.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080130133720.GM7233@v2.random> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1818 Lines: 40 On Wed, Jan 30, 2008 at 02:37:20PM +0100, Andrea Arcangeli wrote: > On Tue, Jan 29, 2008 at 06:28:05PM -0600, Jack Steiner wrote: > > On Tue, Jan 29, 2008 at 04:20:50PM -0800, Christoph Lameter wrote: > > > On Wed, 30 Jan 2008, Andrea Arcangeli wrote: > > > > > > > > invalidate_range after populate allows access to memory for which ptes > > > > > were zapped and the refcount was released. > > > > > > > > The last refcount is released by the invalidate_range itself. > > > > > > That is true for your implementation and to address Robin's issues. Jack: > > > Is that true for the GRU? > > > > I'm not sure I understand the question. The GRU never (currently) takes > > a reference on a page. It has no mechanism for tracking pages that > > were exported to the external TLBs. > > If you don't have a pin, then things like invalidate_range in > remap_file_pages can't be safe as writes through the external TLBs can > keep going on pages in the freelist. For you to be safe w/o a > page-pin, you need to return in the direction of invalidate_page > inside ptep_clear_flush (or anyway before > page_cache_release/__free_page/put_page...). You're generally not safe > with any invalidate_range that may run after the page pointed by the > pte has been freed (or can be freed by the VM anytime because of being > unpinned cache). Yuck.... I see what you mean. I need to review to mail to see why this changed but in the original discussions with Christoph, the invalidate_range callouts were suppose to be made BEFORE the pages were put on the freelist. --- jack -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/