From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A76FC0044C for ; Mon, 5 Nov 2018 09:28:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3875420869 for ; Mon, 5 Nov 2018 09:28:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3875420869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727094AbeKESrl (ORCPT ); Mon, 5 Nov 2018 13:47:41 -0500 Received: from mx2.suse.de ([195.135.220.15]:55732 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726186AbeKESrk (ORCPT ); Mon, 5 Nov 2018 13:47:40 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B904AADE6; Mon, 5 Nov 2018 09:28:51 +0000 (UTC) Date: Mon, 5 Nov 2018 10:28:51 +0100 From: Michal Hocko To: Baoquan He Cc: Andrew Morton , linux-mm@kvack.org, LKML , Stable tree Subject: Re: [PATCH] mm, memory_hotplug: teach has_unmovable_pages about of LRU migrateable pages Message-ID: <20181105092851.GD4361@dhcp22.suse.cz> References: <20181101091055.GA15166@MiWiFi-R3L-srv> <20181102155528.20358-1-mhocko@kernel.org> <20181105002009.GF27491@MiWiFi-R3L-srv> <20181105091407.GB4361@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181105091407.GB4361@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 05-11-18 10:14:07, Michal Hocko wrote: > Maybe we can add a retry for movable zone pages. Or something like this. Ugly as hell, no question about that. I also have to think about this some more to convince myself this will not result in an endless loop under some situations. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 48ceda313332..342d66eca0f3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7779,12 +7779,16 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { unsigned long check = pfn + iter; + unsigned long saved_flags; if (!pfn_valid_within(check)) continue; page = pfn_to_page(check); +retry: + saved_flags = READ_ONCE(page->flags); + if (PageReserved(page)) goto unmovable; @@ -7840,6 +7844,13 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page->mapping->a_ops->migratepage) continue; + /* + * We might race with the allocation of the page so retry + * if flags have changed. + */ + if (saved_flags != READ_ONCE(page->flags)) + goto retry; + /* * If there are RECLAIMABLE pages, we need to check * it. But now, memory offline itself doesn't call -- Michal Hocko SUSE Labs