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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,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 C657AECDFAA for ; Mon, 16 Jul 2018 16:10:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BE9D20BED for ; Mon, 16 Jul 2018 16:10:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BE9D20BED 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 S1728550AbeGPQiE (ORCPT ); Mon, 16 Jul 2018 12:38:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:47640 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727514AbeGPQiE (ORCPT ); Mon, 16 Jul 2018 12:38:04 -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 CE95FAF41; Mon, 16 Jul 2018 16:09:57 +0000 (UTC) Date: Mon, 16 Jul 2018 18:09:56 +0200 From: Michal Hocko To: Pavel Tatashin Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mgorman@techsingularity.net, torvalds@linux-foundation.org, gregkh@linuxfoundation.org Subject: Re: [PATCH] mm: don't do zero_resv_unavail if memmap is not allocated Message-ID: <20180716160956.GW17280@dhcp22.suse.cz> References: <20180716151630.770-1-pasha.tatashin@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180716151630.770-1-pasha.tatashin@oracle.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 16-07-18 11:16:30, Pavel Tatashin wrote: > Moving zero_resv_unavail before memmap_init_zone(), caused a regression on > x86-32. > > The cause is that we access struct pages before they are allocated when > CONFIG_FLAT_NODE_MEM_MAP is used. > > free_area_init_nodes() > zero_resv_unavail() > mm_zero_struct_page(pfn_to_page(pfn)); <- struct page is not alloced > free_area_init_node() > if CONFIG_FLAT_NODE_MEM_MAP > alloc_node_mem_map() > memblock_virt_alloc_node_nopanic() <- struct page alloced here > > On the other hand memblock_virt_alloc_node_nopanic() zeroes all the memory > that it returns, so we do not need to do zero_resv_unavail() here. This all is subtle as hell and almost impossible to build a sane code on top. Your patch sounds good as a stop gap fix but we really need something resembling an actual design rather than ad-hoc hacks piled on top of each other. > Fixes: e181ae0c5db9 ("mm: zero unavailable pages before memmap init") > Signed-off-by: Pavel Tatashin Acked-by: Michal Hocko > --- > include/linux/mm.h | 2 +- > mm/page_alloc.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a0fbb9ffe380..3982c83fdcbf 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2132,7 +2132,7 @@ extern int __meminit __early_pfn_to_nid(unsigned long pfn, > struct mminit_pfnnid_cache *state); > #endif > > -#ifdef CONFIG_HAVE_MEMBLOCK > +#if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP) > void zero_resv_unavail(void); > #else > static inline void zero_resv_unavail(void) {} > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5d800d61ddb7..a790ef4be74e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6383,7 +6383,7 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size, > free_area_init_core(pgdat); > } > > -#ifdef CONFIG_HAVE_MEMBLOCK > +#if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP) > /* > * Only struct pages that are backed by physical memory are zeroed and > * initialized by going through __init_single_page(). But, there are some > @@ -6421,7 +6421,7 @@ void __paginginit zero_resv_unavail(void) > if (pgcnt) > pr_info("Reserved but unavailable: %lld pages", pgcnt); > } > -#endif /* CONFIG_HAVE_MEMBLOCK */ > +#endif /* CONFIG_HAVE_MEMBLOCK && !CONFIG_FLAT_NODE_MEM_MAP */ > > #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP > > -- > 2.18.0 > -- Michal Hocko SUSE Labs