From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753229AbdHKPlE (ORCPT ); Fri, 11 Aug 2017 11:41:04 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:31005 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752631AbdHKPlC (ORCPT ); Fri, 11 Aug 2017 11:41:02 -0400 Subject: Re: [v6 02/15] x86/mm: setting fields in deferred pages To: Michal Hocko Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, kasan-dev@googlegroups.com, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, willy@infradead.org, ard.biesheuvel@linaro.org, will.deacon@arm.com, catalin.marinas@arm.com, sam@ravnborg.org References: <1502138329-123460-1-git-send-email-pasha.tatashin@oracle.com> <1502138329-123460-3-git-send-email-pasha.tatashin@oracle.com> <20170811090214.GD30811@dhcp22.suse.cz> From: Pasha Tatashin Message-ID: Date: Fri, 11 Aug 2017 11:39:41 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170811090214.GD30811@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > AFAIU register_page_bootmem_info_node is only about struct pages backing > pgdat, usemap and memmap. Those should be in reserved memblocks and we > do not initialize those at later times, they are not relevant to the > deferred initialization as your changelog suggests so the ordering with > get_page_bootmem shouldn't matter. Or am I missing something here? The pages for pgdata, usemap, and memmap are part of reserved, and thus getting initialized when free_all_bootmem() is called. So, we have something like this in mem_init() register_page_bootmem_info register_page_bootmem_info_node get_page_bootmem .. setting fields here .. such as: page->freelist = (void *)type; free_all_bootmem() free_low_memory_core_early() for_each_reserved_mem_region() reserve_bootmem_region() init_reserved_page() <- Only if this is deferred reserved page __init_single_pfn() __init_single_page() memset(0) <-- Loose the set fields here! memblock does not know about deferred pages, and can be requested to allocate physical pages anywhere. So, the reserved pages in memblock can be both in non-deferred and deferred part of the memory. Without deferred pages enabled, by the time register_page_bootmem_info() is called every page went through __init_single_page(), but with deferred pages enabled, there is scenario where fields can be set before pages go through __init_single_page(). This patch fixes it.