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 ESMTP id 054CF6B0225 for ; Thu, 6 May 2010 21:43:41 -0400 (EDT) Date: Thu, 6 May 2010 18:40:39 -0700 (PDT) From: Linus Torvalds Subject: Re: [PATCH 2/2] mm,migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack In-Reply-To: <1273188053-26029-3-git-send-email-mel@csn.ul.ie> Message-ID: References: <1273188053-26029-1-git-send-email-mel@csn.ul.ie> <1273188053-26029-3-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Linux-MM , LKML , Minchan Kim , KAMEZAWA Hiroyuki , Christoph Lameter , Andrea Arcangeli , Rik van Riel , Peter Zijlstra List-ID: On Fri, 7 May 2010, Mel Gorman wrote: > > Page migration requires rmap to be able to find all migration ptes > created by migration. If the second rmap_walk clearing migration PTEs > misses an entry, it is left dangling causing a BUG_ON to trigger during > fault. For example; So I still absolutely detest this patch. Why didn't the other - much simpler - patch work? The one Rik pointed to: http://lkml.org/lkml/2010/4/30/198 and didn't do that _disgusting_ temporary anon_vma? Alternatively, why don't we just take the anon_vma lock over this region, so that rmap can't _walk_ the damn thing? Linus -- 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/ . Don't email: email@kvack.org