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=-15.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 1BC0BC433DB for ; Thu, 25 Feb 2021 15:59:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 868E664F1B for ; Thu, 25 Feb 2021 15:59:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 868E664F1B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CC55D6B0005; Thu, 25 Feb 2021 10:59:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C4E536B0070; Thu, 25 Feb 2021 10:59:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF0478D0001; Thu, 25 Feb 2021 10:59:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0178.hostedemail.com [216.40.44.178]) by kanga.kvack.org (Postfix) with ESMTP id 92E586B0005 for ; Thu, 25 Feb 2021 10:59:29 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 54536180DC669 for ; Thu, 25 Feb 2021 15:59:29 +0000 (UTC) X-FDA: 77857250058.16.AB82269 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf12.hostedemail.com (Postfix) with ESMTP id 8D46B13A for ; Thu, 25 Feb 2021 15:59:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614268768; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TqEs2s9NIJ3mhMA0+/qlDylBOaw6l4Ll6nMq3B0MxfE=; b=b5EF6q0+amub7bsDQw0qTjHNFUbhS5pe3ODUWPDixD6TBGD5EuaNDZPqU+OhPKbS+MZScl NqDmyimYhlAFyStP/yyQ5HtceLRvKdvNyWVAsNN0gRfy/MMaWov8BCJhgT+J5g8qEtR5Qf mP2Sh0/pbB7RmMYN19WzTw0lKYcScOo= 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-203-31PQjnKxPSmTSlKR5Bx0sA-1; Thu, 25 Feb 2021 10:59:23 -0500 X-MC-Unique: 31PQjnKxPSmTSlKR5Bx0sA-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 0CD43107ACC7; Thu, 25 Feb 2021 15:59:20 +0000 (UTC) Received: from [10.36.114.58] (ovpn-114-58.ams2.redhat.com [10.36.114.58]) by smtp.corp.redhat.com (Postfix) with ESMTP id E74696EF76; Thu, 25 Feb 2021 15:59:06 +0000 (UTC) To: Mike Rapoport , Andrew Morton Cc: Andrea Arcangeli , Baoquan He , Borislav Petkov , Chris Wilson , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , =?UTF-8?Q?=c5=81ukasz_Majczak?= , Mel Gorman , Michal Hocko , Mike Rapoport , Qian Cai , "Sarvela, Tomi P" , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org References: <20210224153950.20789-1-rppt@kernel.org> <20210224153950.20789-2-rppt@kernel.org> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout Message-ID: <515b4abf-ff07-a43a-ac2e-132c33681886@redhat.com> Date: Thu, 25 Feb 2021 16:59:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210224153950.20789-2-rppt@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8D46B13A X-Stat-Signature: 38e49jxggs3tcy397eg9os3wu4q95631 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614268762-701362 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 24.02.21 16:39, Mike Rapoport wrote: > From: Mike Rapoport >=20 > There could be struct pages that are not backed by actual physical memo= ry. > This can happen when the actual memory bank is not a multiple of > SECTION_SIZE or when an architecture does not register memory holes > reserved by the firmware as memblock.memory. >=20 > Such pages are currently initialized using init_unavailable_mem() funct= ion > that iterates through PFNs in holes in memblock.memory and if there is = a > struct page corresponding to a PFN, the fields of this page are set to > default values and it is marked as Reserved. >=20 > init_unavailable_mem() does not take into account zone and node the pag= e > belongs to and sets both zone and node links in struct page to zero. >=20 > Before commit 73a6e474cb37 ("mm: memmap_init: iterate over memblock reg= ions > rather that check each PFN") the holes inside a zone were re-initialize= d > during memmap_init() and got their zone/node links right. However, afte= r > that commit nothing updates the struct pages representing such holes. >=20 > On a system that has firmware reserved holes in a zone above ZONE_DMA, = for > instance in a configuration below: >=20 > # grep -A1 E820 /proc/iomem > 7a17b000-7a216fff : Unknown E820 type > 7a217000-7bffffff : System RAM >=20 > unset zone link in struct page will trigger >=20 > VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); >=20 > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone lin= k > in struct page) in the same pageblock. >=20 > Interleave initialization of the unavailable pages with the normal > initialization of memory map, so that zone and node information will be > properly set on struct pages that are not backed by the actual memory. >=20 > With this change the pages for holes inside a zone will get proper > zone/node links and the pages that are not spanned by any node will get > links to the adjacent zone/node. >=20 > Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions ra= ther that check each PFN") > Signed-off-by: Mike Rapoport > Reported-by: Qian Cai > Reported-by: Andrea Arcangeli > Reviewed-by: Baoquan He > --- > mm/page_alloc.c | 147 +++++++++++++++++++++--------------------------= - > 1 file changed, 64 insertions(+), 83 deletions(-) >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3e93f8b29bae..a11a9acde708 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6280,12 +6280,60 @@ static void __meminit zone_init_free_lists(stru= ct zone *zone) > } > } > =20 > +#if !defined(CONFIG_FLAT_NODE_MEM_MAP) > +/* > + * Only struct pages that correspond to ranges defined by memblock.mem= ory > + * are zeroed and initialized by going through __init_single_page() du= ring > + * memmap_init_zone(). > + * > + * But, there could be struct pages that correspond to holes in > + * memblock.memory. This can happen because of the following reasons: > + * - phyiscal memory bank size is not necessarily the exact multiple o= f the > + * arbitrary section size > + * - early reserved memory may not be listed in memblock.memory > + * - memory layouts defined with memmap=3D kernel parameter may not al= ign > + * nicely with memmap sections > + * > + * Explicitly initialize those struct pages so that: > + * - PG_Reserved is set > + * - zone and node links point to zone and node that span the page > + */ > +static u64 __meminit init_unavailable_range(unsigned long spfn, > + unsigned long epfn, > + int zone, int node) > +{ > + unsigned long pfn; > + u64 pgcnt =3D 0; > + > + for (pfn =3D spfn; pfn < epfn; pfn++) { > + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { > + pfn =3D ALIGN_DOWN(pfn, pageblock_nr_pages) > + + pageblock_nr_pages - 1; > + continue; > + } > + __init_single_page(pfn_to_page(pfn), pfn, zone, node); > + __SetPageReserved(pfn_to_page(pfn)); > + pgcnt++; > + } > + > + return pgcnt; > +} > +#else > +static inline u64 init_unavailable_range(unsigned long spfn, unsigned = long epfn, > + int zone, int node) > +{ > + return 0; > +} > +#endif > + > void __meminit __weak memmap_init_zone(struct zone *zone) > { > unsigned long zone_start_pfn =3D zone->zone_start_pfn; > unsigned long zone_end_pfn =3D zone_start_pfn + zone->spanned_pages; > int i, nid =3D zone_to_nid(zone), zone_id =3D zone_idx(zone); > + static unsigned long hole_pfn =3D 0; > unsigned long start_pfn, end_pfn; > + u64 pgcnt =3D 0; > =20 > for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) { > start_pfn =3D clamp(start_pfn, zone_start_pfn, zone_end_pfn); > @@ -6295,7 +6343,23 @@ void __meminit __weak memmap_init_zone(struct zo= ne *zone) > memmap_init_range(end_pfn - start_pfn, nid, > zone_id, start_pfn, zone_end_pfn, > MEMINIT_EARLY, NULL, MIGRATE_MOVABLE); > + > + if (hole_pfn < start_pfn) > + pgcnt +=3D init_unavailable_range(hole_pfn, start_pfn, > + zone_id, nid); > + hole_pfn =3D end_pfn; > } > + > +#ifdef CONFIG_SPARSEMEM > + end_pfn =3D round_up(zone_end_pfn, PAGES_PER_SECTION); > + if (hole_pfn < end_pfn) > + pgcnt +=3D init_unavailable_range(hole_pfn, end_pfn, > + zone_id, nid); We might still double-initialize PFNs when two zones overlap within a=20 section, correct? This might worth documenting - also, you might want to=20 take some of the original comment the accompanied this code. You should also document (in the patch description?) that node/zone=20 spans are not properly handled yet for such hole pfns and that this=20 might require care in the future. I played a little with weird setups and expected the memap state using=20 page-types (well, I can't inspect the node/zone that way but at least=20 have a look if the memmap was initialized). No surprises. --=20 Thanks, David / dhildenb