From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755981Ab0KSRkS (ORCPT ); Fri, 19 Nov 2010 12:40:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52427 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755658Ab0KSRkQ (ORCPT ); Fri, 19 Nov 2010 12:40:16 -0500 Date: Fri, 19 Nov 2010 18:38:17 +0100 From: Andrea Arcangeli To: Mel Gorman Cc: linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, KOSAKI Motohiro , Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov Subject: Re: [PATCH 02 of 66] mm, migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack Message-ID: <20101119173817.GE24450@random.random> References: <20101118111349.GG8135@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101118111349.GG8135@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 18, 2010 at 11:13:49AM +0000, Mel Gorman wrote: > This old chestnut. IIRC, this was the more complete solution to a fix that made > it into mainline. The patch still looks reasonable. It does add a kmalloc() > but I can't remember if we decided we were ok with it or not. Can you remind We decided the kmalloc was ok, but Linus didn't like this approach. I kept it in my tree because I didn't want to remember when/if to add the special check in the accurate rmap walks. I find it simpler if all rmap walks are accurate by default. > me? More importantly, it appears to be surviving the original testcase that > this bug was about (20 minutes so far but will leave it a few hours). Assuming > the test does not crash; Sure the patch is safe. If Linus still doesn't like this, I will immediately remove this patch and add the special checks to the rmap walks in huge_memory.c, you know my preference but this is a detail and my preference is irrelevant. Thanks, Andrea From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id CC60B6B0071 for ; Fri, 19 Nov 2010 12:39:34 -0500 (EST) Date: Fri, 19 Nov 2010 18:38:17 +0100 From: Andrea Arcangeli Subject: Re: [PATCH 02 of 66] mm, migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack Message-ID: <20101119173817.GE24450@random.random> References: <20101118111349.GG8135@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101118111349.GG8135@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, KOSAKI Motohiro , Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov List-ID: On Thu, Nov 18, 2010 at 11:13:49AM +0000, Mel Gorman wrote: > This old chestnut. IIRC, this was the more complete solution to a fix that made > it into mainline. The patch still looks reasonable. It does add a kmalloc() > but I can't remember if we decided we were ok with it or not. Can you remind We decided the kmalloc was ok, but Linus didn't like this approach. I kept it in my tree because I didn't want to remember when/if to add the special check in the accurate rmap walks. I find it simpler if all rmap walks are accurate by default. > me? More importantly, it appears to be surviving the original testcase that > this bug was about (20 minutes so far but will leave it a few hours). Assuming > the test does not crash; Sure the patch is safe. If Linus still doesn't like this, I will immediately remove this patch and add the special checks to the rmap walks in huge_memory.c, you know my preference but this is a detail and my preference is irrelevant. Thanks, Andrea -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org