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=-15.7 required=3.0 tests=BAYES_00, 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 0A714C433E9 for ; Thu, 25 Feb 2021 17:51:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6587D64F41 for ; Thu, 25 Feb 2021 17:51:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6587D64F41 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EABF58D0001; Thu, 25 Feb 2021 12:51:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E59B46B006E; Thu, 25 Feb 2021 12:51:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D221F8D0001; Thu, 25 Feb 2021 12:51:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0162.hostedemail.com [216.40.44.162]) by kanga.kvack.org (Postfix) with ESMTP id BB2F46B006C for ; Thu, 25 Feb 2021 12:51:56 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 78FCEAF75 for ; Thu, 25 Feb 2021 17:51:56 +0000 (UTC) X-FDA: 77857533432.23.F1960A2 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf28.hostedemail.com (Postfix) with ESMTP id B919220001EA for ; Thu, 25 Feb 2021 17:51:55 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 37A0BAD57; Thu, 25 Feb 2021 17:51:54 +0000 (UTC) To: Mike Rapoport , Andrew Morton Cc: Andrea Arcangeli , Baoquan He , Borislav Petkov , Chris Wilson , David Hildenbrand , "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 , 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: Vlastimil Babka Subject: Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout Message-ID: Date: Thu, 25 Feb 2021 18:51:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210224153950.20789-2-rppt@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B919220001EA X-Stat-Signature: jhhftgby84p8xf7qufhhhejgeo1frkbh Received-SPF: none (suse.cz>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1614275515-925193 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 2/24/21 4:39 PM, Mike Rapoport wrote: > From: Mike Rapoport Hi, thanks for your efforts. I'll just nit pick on the description/commen= ts as I don't feel confident about judging the implementation correctness, sorry = :) > 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); ... in set_pfnblock_flags_mask() when called with a struct page from the "Unknown E820 type" range. > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone lin= k > in struct page) in the same pageblock. I would say "there are apparently pages" ... "and ZONE_DMA does not span = this range" > 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. What if two zones are adjacent? I.e. if the hole was at a boundary betwee= n two zones. > 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 For the approach: Acked-by: Vlastimil Babka > --- > 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 physical > + * 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 Yes spanned pages are the most important, but should you also describe he= re the adjacent ones, as you do in commit log? > + */ > +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); > +#endif > + > + if (pgcnt) > + pr_info(" %s zone: %lld pages in unavailable ranges\n", > + zone->name, pgcnt); > } > =20 > static int zone_batchsize(struct zone *zone) > @@ -7092,88 +7156,6 @@ void __init free_area_init_memoryless_node(int n= id) > free_area_init_node(nid); > } > =20 > -#if !defined(CONFIG_FLAT_NODE_MEM_MAP) > -/* > - * Initialize all valid struct pages in the range [spfn, epfn) and mar= k them > - * PageReserved(). Return the number of struct pages that were initial= ized. > - */ > -static u64 __init init_unavailable_range(unsigned long spfn, unsigned = long epfn) > -{ > - 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; > - } > - /* > - * Use a fake node/zone (0) for now. Some of these pages > - * (in memblock.reserved but not in memblock.memory) will > - * get re-initialized via reserve_bootmem_region() later. > - */ > - __init_single_page(pfn_to_page(pfn), pfn, 0, 0); > - __SetPageReserved(pfn_to_page(pfn)); > - pgcnt++; > - } > - > - return pgcnt; > -} > - > -/* > - * Only struct pages that are backed by physical memory are zeroed and > - * initialized by going through __init_single_page(). But, there are s= ome > - * struct pages which are reserved in memblock allocator and their fie= lds > - * may be accessed (for example page_to_pfn() on some configuration ac= cesses > - * flags). We must explicitly initialize those struct pages. > - * > - * This function also addresses a similar issue where struct pages are= left > - * uninitialized because the physical address range is not covered by > - * memblock.memory or memblock.reserved. That could happen when memblo= ck > - * layout is manually configured via memmap=3D, or when the highest ph= ysical > - * address (max_pfn) does not end on a section boundary. > - */ > -static void __init init_unavailable_mem(void) > -{ > - phys_addr_t start, end; > - u64 i, pgcnt; > - phys_addr_t next =3D 0; > - > - /* > - * Loop through unavailable ranges not covered by memblock.memory. > - */ > - pgcnt =3D 0; > - for_each_mem_range(i, &start, &end) { > - if (next < start) > - pgcnt +=3D init_unavailable_range(PFN_DOWN(next), > - PFN_UP(start)); > - next =3D end; > - } > - > - /* > - * Early sections always have a fully populated memmap for the whole > - * section - see pfn_valid(). If the last section has holes at the > - * end and that section is marked "online", the memmap will be > - * considered initialized. Make sure that memmap has a well defined > - * state. > - */ > - pgcnt +=3D init_unavailable_range(PFN_DOWN(next), > - round_up(max_pfn, PAGES_PER_SECTION)); > - > - /* > - * Struct pages that do not have backing memory. This could be becaus= e > - * firmware is using some of this memory, or for some other reasons. > - */ > - if (pgcnt) > - pr_info("Zeroed struct page in unavailable ranges: %lld pages", pgcn= t); > -} > -#else > -static inline void __init init_unavailable_mem(void) > -{ > -} > -#endif /* !CONFIG_FLAT_NODE_MEM_MAP */ > - > #if MAX_NUMNODES > 1 > /* > * Figure out the number of possible node ids. > @@ -7597,7 +7579,6 @@ void __init free_area_init(unsigned long *max_zon= e_pfn) > /* Initialise every node */ > mminit_verify_pageflags_layout(); > setup_nr_node_ids(); > - init_unavailable_mem(); > for_each_online_node(nid) { > pg_data_t *pgdat =3D NODE_DATA(nid); > free_area_init_node(nid); >=20