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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D77D2C433EF for ; Fri, 18 Mar 2022 06:40:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 447AA8D0002; Fri, 18 Mar 2022 02:40:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F74B8D0001; Fri, 18 Mar 2022 02:40:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E4E68D0002; Fri, 18 Mar 2022 02:40:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 1E6678D0001 for ; Fri, 18 Mar 2022 02:40:45 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id DB83124DA1 for ; Fri, 18 Mar 2022 06:40:44 +0000 (UTC) X-FDA: 79256558808.07.EDBD023 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf31.hostedemail.com (Postfix) with ESMTP id 88DD920016 for ; Fri, 18 Mar 2022 06:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1647585643; x=1679121643; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=59ehILCdsEIgUfsRNpzm4hT+4CUyYxmwDaIHVsIX8s0=; b=MIGEtHRSl7QgPRIzyXJ+0lktBR1CG+TmcmwPN77Z/8Ei5g0MaHjUUiY2 f0zAnKeOeVU4yuhpw+dBPFxHSq5PqJPi6z4rEtk3T1i4DA63sQi+aN3FM 4UX7Ye/Q3oAAw1Ie/Q8Z2hvTLUoFXEw9x2/bfBF4xqQBWDXaLcAHQRMLH ryhEgAwhPvhpXe0snLQdD8NKLuwN5BzSNe1HpLxojPv4oE9zH2DYad+hC IVwADPMEEoy5i6YO4e1g0whg3MLkwSYW00wEoPgtWiu7dX5NVpfxV6t32 x4ZbailemzPRfnMmGGkqWN1ZeYKKrB+uT1fwK55OlyXI2dgcZ0Q/ujalt w==; X-IronPort-AV: E=McAfee;i="6200,9189,10289"; a="343504460" X-IronPort-AV: E=Sophos;i="5.90,191,1643702400"; d="scan'208";a="343504460" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2022 23:40:42 -0700 X-IronPort-AV: E=Sophos;i="5.90,191,1643702400"; d="scan'208";a="558280308" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.13.94]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2022 23:40:38 -0700 From: "Huang, Ying" To: Miaohe Lin Cc: , , , , , , Subject: Re: [PATCH v2 11/11] mm/migration: fix possible do_pages_stat_array racing with memory offline References: <20220318111709.60311-1-linmiaohe@huawei.com> <20220318111709.60311-12-linmiaohe@huawei.com> Date: Fri, 18 Mar 2022 14:40:36 +0800 In-Reply-To: <20220318111709.60311-12-linmiaohe@huawei.com> (Miaohe Lin's message of "Fri, 18 Mar 2022 19:17:09 +0800") Message-ID: <878rt7oja3.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 88DD920016 X-Stat-Signature: zpmjugwahmnaefm7zyydn7qxenbmbg9z X-Rspam-User: Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=MIGEtHRS; spf=none (imf31.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=ying.huang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-HE-Tag: 1647585643-864703 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: Miaohe Lin writes: > When follow_page peeks a page, the page could be migrated and then be > offlined while it's still being used by the do_pages_stat_array(). > Use FOLL_GET to hold the page refcnt to fix this potential race. > > Signed-off-by: Miaohe Lin Acked-by: "Huang, Ying" > --- > mm/migrate.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index dbd91fbdb127..cd85ba0ab592 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1807,13 +1807,18 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > goto set_status; > > /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_DUMP); > + page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > > err = PTR_ERR(page); > if (IS_ERR(page)) > goto set_status; > > - err = page ? page_to_nid(page) : -ENOENT; > + if (page) { > + err = page_to_nid(page); > + put_page(page); > + } else { > + err = -ENOENT; > + } > set_status: > *status = err;