From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752050AbeA2XjL (ORCPT ); Mon, 29 Jan 2018 18:39:11 -0500 Received: from mail-co1nam03on0095.outbound.protection.outlook.com ([104.47.40.95]:28928 "EHLO NAM03-CO1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751417AbeA2XjJ (ORCPT ); Mon, 29 Jan 2018 18:39:09 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=zi.yan@cs.rutgers.edu; From: "Zi Yan" To: "Andrew Morton" Cc: "Michal Hocko" , "Naoya Horiguchi" , "Kirill A. Shutemov" , "Vlastimil Babka" , "Andrea Reale" , "Anshuman Khandual" , linux-mm@kvack.org, LKML , "Michal Hocko" Subject: Re: [PATCH 1/3] mm, numa: rework do_pages_move Date: Mon, 29 Jan 2018 18:39:01 -0500 X-Mailer: MailMate (2.0BETAr6103) Message-ID: <07425013-A7A9-4BB8-8FAA-9581D966A29B@cs.rutgers.edu> In-Reply-To: <20180129143522.68a5332ae80d28461441a6be@linux-foundation.org> References: <20180103082555.14592-1-mhocko@kernel.org> <20180103082555.14592-2-mhocko@kernel.org> <8ECFD324-D8A0-47DC-A6FD-B9F7D29445DC@cs.rutgers.edu> <20180129143522.68a5332ae80d28461441a6be@linux-foundation.org> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=_MailMate_82629931-A273-4C60-BCE9-285C5743D4F6_="; micalg=pgp-sha512; protocol="application/pgp-signature" X-Originating-IP: [128.6.37.110] X-ClientProxiedBy: BN6PR13CA0037.namprd13.prod.outlook.com (10.171.172.23) To DM5PR14MB1657.namprd14.prod.outlook.com (10.171.156.15) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 3772d717-b0d3-4669-6dd8-08d567717cc1 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(5600026)(4604075)(2017052603307)(7153060)(7193020);SRVR:DM5PR14MB1657; 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markup=markdown On 29 Jan 2018, at 17:35, Andrew Morton wrote: > On Mon, 29 Jan 2018 17:06:14 -0500 "Zi Yan" wrote: > >> I discover that this patch does not hold mmap_sem while migrating pages in >> do_move_pages_to_node(). >> >> A simple fix below moves mmap_sem from add_page_for_migration() >> to the outmost do_pages_move(): > > I'm not surprised. Why does do_move_pages_to_node() need mmap_sem > and how is a reader to discover that fact??? do_move_pages_to_node() calls migrate_pages(), which requires down_read(&mmap_sem). In the outmost do_pages_move(), both add_page_for_migration() and do_move_pages_to_node() inside it need to hold read lock of mmap_sem. Do we need to add comments for both functions? -- Best Regards Yan Zi --=_MailMate_82629931-A273-4C60-BCE9-285C5743D4F6_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQEcBAEBCgAGBQJab7CWAAoJEEGLLxGcTqbMSAgH/2/8yCgR0MfGqZ4rDG4zFlZo RTL+u7K/cqT3ATheAn2OUrFXIN1PvYnQMtWTZlxD3/UwwiVAVNBjOPgvNfsH8pBU wYpUhLZelY+7eDh76w1gjbXX3mLj8aw/G6iElT9Bn+E2rpdNAGEWIVpRvlCfJhuC namOqKF0O6XmmnInbkjtDpjts2i7I4MRmGF68uHMDUVC22V/rAkG58frdd8ebpi+ 2tjh46d8VftAkNSldAppmhh1CuQzrrrCqmy7cKWh93mmsMCN6ulVjduONZUr9Wu+ 8yWLrK/2imgApk30vcR6avcG63uqUylvzzBNg8z+5za0WLu+oFrxhicpf3jaHL0= =PsUi -----END PGP SIGNATURE----- --=_MailMate_82629931-A273-4C60-BCE9-285C5743D4F6_=--