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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 007B2C4CECD for ; Tue, 17 Sep 2019 09:58:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 96C67214AF for ; Tue, 17 Sep 2019 09:58:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96C67214AF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=vx.jp.nec.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 011B76B0003; Tue, 17 Sep 2019 05:58:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F03386B0005; Tue, 17 Sep 2019 05:58:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E19F66B0006; Tue, 17 Sep 2019 05:58:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0241.hostedemail.com [216.40.44.241]) by kanga.kvack.org (Postfix) with ESMTP id C04CE6B0003 for ; Tue, 17 Sep 2019 05:58:07 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 679EC180AD802 for ; Tue, 17 Sep 2019 09:58:07 +0000 (UTC) X-FDA: 75943961814.25.whip01_29a8f9f6caa23 X-HE-Tag: whip01_29a8f9f6caa23 X-Filterd-Recvd-Size: 5042 Received: from tyo161.gate.nec.co.jp (tyo161.gate.nec.co.jp [114.179.232.161]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Tue, 17 Sep 2019 09:58:05 +0000 (UTC) Received: from mailgate01.nec.co.jp ([114.179.233.122]) by tyo161.gate.nec.co.jp (8.15.1/8.15.1) with ESMTPS id x8H9vshM011512 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 17 Sep 2019 18:57:54 +0900 Received: from mailsv01.nec.co.jp (mailgate-v.nec.co.jp [10.204.236.94]) by mailgate01.nec.co.jp (8.15.1/8.15.1) with ESMTP id x8H9vsdV024649; Tue, 17 Sep 2019 18:57:54 +0900 Received: from mail01b.kamome.nec.co.jp (mail01b.kamome.nec.co.jp [10.25.43.2]) by mailsv01.nec.co.jp (8.15.1/8.15.1) with ESMTP id x8H9uoda001377; Tue, 17 Sep 2019 18:57:54 +0900 Received: from bpxc99gp.gisp.nec.co.jp ([10.38.151.148] [10.38.151.148]) by mail03.kamome.nec.co.jp with ESMTP id BT-MMP-1171633; Tue, 17 Sep 2019 18:32:44 +0900 Received: from BPXM20GP.gisp.nec.co.jp ([10.38.151.212]) by BPXC20GP.gisp.nec.co.jp ([10.38.151.148]) with mapi id 14.03.0439.000; Tue, 17 Sep 2019 18:32:44 +0900 From: Toshiki Fukasawa To: David Hildenbrand , "linux-mm@kvack.org" , "dan.j.williams@intel.com" CC: Toshiki Fukasawa , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "mhocko@kernel.org" , "adobriyan@gmail.com" , "hch@lst.de" , "longman@redhat.com" , "sfr@canb.auug.org.au" , "mst@redhat.com" , Naoya Horiguchi , Junichi Nomura Subject: Re: [RFC PATCH v2] mm: initialize struct pages reserved by ZONE_DEVICE driver. Thread-Topic: [RFC PATCH v2] mm: initialize struct pages reserved by ZONE_DEVICE driver. Thread-Index: AQHVZIp2xk1cU6nEkk+ez7kL5reVFKcdvuyAgAAVnwCAAAk8gIAEZuMAgAAgogCADDvdgIAATZsAgAAnMAA= Date: Tue, 17 Sep 2019 09:32:43 +0000 Message-ID: <3d27953a-88b8-5a7c-de3c-041f8b4436f6@vx.jp.nec.com> References: <20190906081027.15477-1-t-fukasawa@vx.jp.nec.com> <40a1ce2e-1384-b869-97d0-7195b5b47de0@redhat.com> <6a99e003-e1ab-b9e8-7b25-bc5605ab0eb2@vx.jp.nec.com> <31fd3c86-5852-1863-93bd-8df9da9f95b4@vx.jp.nec.com> <38e58d23-c20b-4e68-5f56-20bba2be2d6c@redhat.com> In-Reply-To: <38e58d23-c20b-4e68-5f56-20bba2be2d6c@redhat.com> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.34.125.135] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-TM-AS-MML: disable X-Bogosity: Ham, tests=bogofilter, spamicity=0.001890, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2019/09/17 16:13, David Hildenbrand wrote: > On 17.09.19 04:34, Toshiki Fukasawa wrote: >> On 2019/09/09 16:46, David Hildenbrand wrote: >>> Let's take a step back here to understand the issues I am aware of. I >>> think we should solve this for good now: >>> >>> A PFN walker takes a look at a random PFN at a random point in time. It >>> finds a PFN with SECTION_MARKED_PRESENT && !SECTION_IS_ONLINE. The >>> options are: >>> >>> 1. It is buddy memory (add_memory()) that has not been online yet. The >>> memmap contains garbage. Don't access. >>> >>> 2. It is ZONE_DEVICE memory with a valid memmap. Access it. >>> >>> 3. It is ZONE_DEVICE memory with an invalid memmap, because the section >>> is only partially present: E.g., device starts at offset 64MB within a >>> section or the device ends at offset 64MB within a section. Don't acces= s it. >> >> I don't agree with case #3. In the case, struct page area is not allocat= ed on >> ZONE_DEVICE, but is allocated on system memory. So I think we can access= the >> struct pages. What do you mean "invalid memmap"? > No, that's not the case. There is no memory, especially not system > memory. We only allow partially present sections (sub-section memory > hotplug) for ZONE_DEVICE. Let me clear my thoughts. If I read correctly, the struct pages for section= s (including partially present sections) on ZONE_DEVICE are allocated by vmemmap_populate(). And all the struct pages except (altmap->base_pfn) to (altmap->base_pfn + altmap->reserve) are initialized by memmap_init_zone() and memmap_init_zone_device(). Do struct pages for partially present sections go through a different proce= ss? Thanks, Toshiki Fukasawa >=20 > invalid memmap =3D=3D memmap was not initialized =3D=3D struct pages cont= ains > garbage. There is a memmap, but accessing it (e.g., pfn_to_nid()) will > trigger a BUG. > =