From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933535Ab3LIOIv (ORCPT ); Mon, 9 Dec 2013 09:08:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:24144 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932663Ab3LIOIs (ORCPT ); Mon, 9 Dec 2013 09:08:48 -0500 Message-ID: <52A5CEE6.2080609@redhat.com> Date: Mon, 09 Dec 2013 09:08:38 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mel Gorman CC: Andrew Morton , Alex Thorlton , Linux-MM , LKML Subject: Re: [PATCH 01/18] mm: numa: Serialise parallel get_user_page against THP migration References: <1386572952-1191-1-git-send-email-mgorman@suse.de> <1386572952-1191-2-git-send-email-mgorman@suse.de> In-Reply-To: <1386572952-1191-2-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/09/2013 02:08 AM, Mel Gorman wrote: > Base pages are unmapped and flushed from cache and TLB during normal page > migration and replaced with a migration entry that causes any parallel or > gup to block until migration completes. THP does not unmap pages due to > a lack of support for migration entries at a PMD level. This allows races > with get_user_pages and get_user_pages_fast which commit 3f926ab94 ("mm: > Close races between THP migration and PMD numa clearing") made worse by > introducing a pmd_clear_flush(). > > This patch forces get_user_page (fast and normal) on a pmd_numa page to > go through the slow get_user_page path where it will serialise against THP > migration and properly account for the NUMA hinting fault. On the migration > side the page table lock is taken for each PTE update. > > Cc: stable@vger.kernel.org > Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel -- All rights reversed