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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 D5A29C43441 for ; Wed, 14 Nov 2018 08:54:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A392922419 for ; Wed, 14 Nov 2018 08:54:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A392922419 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 S1732128AbeKNS4R (ORCPT ); Wed, 14 Nov 2018 13:56:17 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:40244 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727154AbeKNS4R (ORCPT ); Wed, 14 Nov 2018 13:56:17 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D1D10EBD; Wed, 14 Nov 2018 00:53:58 -0800 (PST) Received: from [10.162.42.147] (p8cg001049571a15.blr.arm.com [10.162.42.147]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 15C873F5CF; Wed, 14 Nov 2018 00:53:55 -0800 (PST) Subject: Re: [RFC][PATCH v1 02/11] mm: soft-offline: add missing error check of set_hwpoison_free_buddy_page() To: Naoya Horiguchi Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Michal Hocko , Andrew Morton , Mike Kravetz , "xishi.qiuxishi@alibaba-inc.com" , Laurent Dufour References: <1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1541746035-13408-3-git-send-email-n-horiguchi@ah.jp.nec.com> <9ea93154-4843-231d-d72b-bf12c8807c24@arm.com> <20181113001652.GA5945@hori1.linux.bs1.fc.nec.co.jp> From: Anshuman Khandual Message-ID: Date: Wed, 14 Nov 2018 14:23:52 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181113001652.GA5945@hori1.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset=iso-2022-jp Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/13/2018 05:46 AM, Naoya Horiguchi wrote: > Hi Anshuman, > > On Fri, Nov 09, 2018 at 03:50:41PM +0530, Anshuman Khandual wrote: >> >> On 11/09/2018 12:17 PM, Naoya Horiguchi wrote: >>> set_hwpoison_free_buddy_page() could fail, then the target page is >>> finally not isolated, so it's better to report -EBUSY for userspace >>> to know the failure and chance of retry. >>> >> IIUC set_hwpoison_free_buddy_page() could only fail if the page is not >> free in the buddy. At least for soft_offline_huge_page() that wont be >> the case otherwise dissolve_free_huge_page() would have returned non >> zero -EBUSY. Is there any other reason set_hwpoison_free_buddy_page() >> would not succeed ? > There is a race window between page freeing (after successful soft-offline > -> page migration case) and the containment by set_hwpoison_free_buddy_page(). > Or a target page can be allocated just after get_any_page() decided that > the target page is a free page. > So set_hwpoison_free_buddy_page() would safely fail in such cases. Makes sense. Thanks.