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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 057B7C433E0 for ; Tue, 16 Jun 2020 11:52:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8EB020A8B for ; Tue, 16 Jun 2020 11:52:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ijthp803" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728435AbgFPLwa (ORCPT ); Tue, 16 Jun 2020 07:52:30 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:42127 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725843AbgFPLw2 (ORCPT ); Tue, 16 Jun 2020 07:52:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592308347; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nC4omS0wZXEwgJ3j/b3OR0MRArgteyLwgrhrykedSUg=; b=ijthp803vWOhoLch7kyIuxN4MIGLKy9gQftf7U78IodEU4citWciNlaPKxit03O6NGXtdV B1at2KKla3nAx4iZPy8E0BpiwnL4E1GV3jdQ2BfUYq9FGwxNeYPUDkMvl6WWucD96W27+L 2vGdFvjiD4MmGqBEzaPQ+bi6pHbDME4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-477-ldIpgm-fPC2e1l1xNjvZ9g-1; Tue, 16 Jun 2020 07:52:25 -0400 X-MC-Unique: ldIpgm-fPC2e1l1xNjvZ9g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9300F18585BC; Tue, 16 Jun 2020 11:52:23 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-106.ams2.redhat.com [10.36.114.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6255E7CAA5; Tue, 16 Jun 2020 11:52:21 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , stable@vger.kernel.org, Andrew Morton , Johannes Weiner , Michal Hocko , Minchan Kim , Huang Ying , Wei Yang , Mel Gorman Subject: [PATCH v1 1/3] mm/shuffle: don't move pages between zones and don't read garbage memmaps Date: Tue, 16 Jun 2020 13:52:11 +0200 Message-Id: <20200616115213.13109-2-david@redhat.com> In-Reply-To: <20200616115213.13109-1-david@redhat.com> References: <20200616115213.13109-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Especially with memory hotplug, we can have offline sections (with a garbage memmap) and overlapping zones. We have to make sure to only touch initialized memmaps (online sections managed by the buddy) and that the zone matches, to not move pages between zones. To test if this can actually happen, I added a simple BUG_ON(page_zone(page_i) != page_zone(page_j)); right before the swap. When hotplugging a 256M DIMM to a 4G x86-64 VM and onlining the first memory block "online_movable" and the second memory block "online_kernel", it will trigger the BUG, as both zones (NORMAL and MOVABLE) overlap. This might result in all kinds of weird situations (e.g., double allocations, list corruptions, unmovable allocations ending up in the movable zone). Fixes: e900a918b098 ("mm: shuffle initial free memory to improve memory-side-cache utilization") Cc: stable@vger.kernel.org # v5.2+ Cc: Andrew Morton Cc: Johannes Weiner Cc: Michal Hocko Cc: Minchan Kim Cc: Huang Ying Cc: Wei Yang Cc: Mel Gorman Signed-off-by: David Hildenbrand --- mm/shuffle.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/mm/shuffle.c b/mm/shuffle.c index 44406d9977c77..dd13ab851b3ee 100644 --- a/mm/shuffle.c +++ b/mm/shuffle.c @@ -58,25 +58,25 @@ module_param_call(shuffle, shuffle_store, shuffle_show, &shuffle_param, 0400); * For two pages to be swapped in the shuffle, they must be free (on a * 'free_area' lru), have the same order, and have the same migratetype. */ -static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order) +static struct page * __meminit shuffle_valid_page(struct zone *zone, + unsigned long pfn, int order) { - struct page *page; + struct page *page = pfn_to_online_page(pfn); /* * Given we're dealing with randomly selected pfns in a zone we * need to ask questions like... */ - /* ...is the pfn even in the memmap? */ - if (!pfn_valid_within(pfn)) + /* ... is the page managed by the buddy? */ + if (!page) return NULL; - /* ...is the pfn in a present section or a hole? */ - if (!pfn_in_present_section(pfn)) + /* ... is the page assigned to the same zone? */ + if (page_zone(page) != zone) return NULL; /* ...is the page free and currently on a free_area list? */ - page = pfn_to_page(pfn); if (!PageBuddy(page)) return NULL; @@ -123,7 +123,7 @@ void __meminit __shuffle_zone(struct zone *z) * page_j randomly selected in the span @zone_start_pfn to * @spanned_pages. */ - page_i = shuffle_valid_page(i, order); + page_i = shuffle_valid_page(z, i, order); if (!page_i) continue; @@ -137,7 +137,7 @@ void __meminit __shuffle_zone(struct zone *z) j = z->zone_start_pfn + ALIGN_DOWN(get_random_long() % z->spanned_pages, order_pages); - page_j = shuffle_valid_page(j, order); + page_j = shuffle_valid_page(z, j, order); if (page_j && page_j != page_i) break; } -- 2.26.2