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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 AAEA3CA9EB0 for ; Mon, 21 Oct 2019 14:43:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 812BD2053B for ; Mon, 21 Oct 2019 14:43:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571669030; bh=4tucuf7nmKqmOHZr8VTJCYuBSVagd0+Lf0FuQZjv800=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=acZSVXkaBOduOQLdLIgYTrtV/gxVcecZmK7B1r5HBHRn3Ml5N6mjX/kYsG1TY5rbZ pfoDl2Ga3sFmgf5V6y8vhKHk3G4tys0d/AIe/ylEskxNZWmOl/0d2Z7arwIy8hOvW7 6xdVD0A5qxc5E219hgUIkFmO1Ov8o3DrNBsiNYO4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728167AbfJUOnt (ORCPT ); Mon, 21 Oct 2019 10:43:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:40534 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727822AbfJUOnt (ORCPT ); Mon, 21 Oct 2019 10:43:49 -0400 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 6D9E6B794; Mon, 21 Oct 2019 14:43:46 +0000 (UTC) Date: Mon, 21 Oct 2019 16:43:45 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Oscar Salvador , Mel Gorman , Mike Rapoport , Dan Williams , Wei Yang , Alexander Duyck , Anshuman Khandual , Pavel Tatashin Subject: Re: [PATCH v1 1/2] mm/page_alloc.c: Don't set pages PageReserved() when offlining Message-ID: <20191021144345.GT9379@dhcp22.suse.cz> References: <20191021141927.10252-1-david@redhat.com> <20191021141927.10252-2-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191021141927.10252-2-david@redhat.com> 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 21-10-19 16:19:25, David Hildenbrand wrote: > We call __offline_isolated_pages() from __offline_pages() after all > pages were isolated and are either free (PageBuddy()) or PageHWPoison. > Nothing can stop us from offlining memory at this point. > > In __offline_isolated_pages() we first set all affected memory sections > offline (offline_mem_sections(pfn, end_pfn)), to mark the memmap as > invalid (pfn_to_online_page() will no longer succeed), and then walk over > all pages to pull the free pages from the free lists (to the isolated > free lists, to be precise). > > Note that re-onlining a memory block will result in the whole memmap > getting reinitialized, overwriting any old state. We already poision the > memmap when offlining is complete to find any access to > stale/uninitialized memmaps. > > So, setting the pages PageReserved() is not helpful. The memap is marked > offline and all pageblocks are isolated. As soon as offline, the memmap > is stale either way. > > This looks like a leftover from ancient times where we initialized the > memmap when adding memory and not when onlining it (the pages were set > PageReserved so re-onling would work as expected). > > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Vlastimil Babka > Cc: Oscar Salvador > Cc: Mel Gorman > Cc: Mike Rapoport > Cc: Dan Williams > Cc: Wei Yang > Cc: Alexander Duyck > Cc: Anshuman Khandual > Cc: Pavel Tatashin > Signed-off-by: David Hildenbrand Acked-by: Michal Hocko We still set PageReserved before onlining pages and that one should be good to go as well (memmap_init_zone). Thanks! There is a comment above offline_isolated_pages_cb that should be removed as well. > --- > mm/page_alloc.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ed8884dc0c47..bf6b21f02154 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8667,7 +8667,7 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > { > struct page *page; > struct zone *zone; > - unsigned int order, i; > + unsigned int order; > unsigned long pfn; > unsigned long flags; > unsigned long offlined_pages = 0; > @@ -8695,7 +8695,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > */ > if (unlikely(!PageBuddy(page) && PageHWPoison(page))) { > pfn++; > - SetPageReserved(page); > offlined_pages++; > continue; > } > @@ -8709,8 +8708,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > pfn, 1 << order, end_pfn); > #endif > del_page_from_free_area(page, &zone->free_area[order]); > - for (i = 0; i < (1 << order); i++) > - SetPageReserved((page+i)); > pfn += (1 << order); > } > spin_unlock_irqrestore(&zone->lock, flags); > -- > 2.21.0 > -- Michal Hocko SUSE Labs