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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBA7FC433F5 for ; Wed, 16 Feb 2022 02:13:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343568AbiBPCNe (ORCPT ); Tue, 15 Feb 2022 21:13:34 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:59248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230199AbiBPCN2 (ORCPT ); Tue, 15 Feb 2022 21:13:28 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72A617D000 for ; Tue, 15 Feb 2022 18:13:17 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Jz1bV03xGz1FD0V; Wed, 16 Feb 2022 10:08:54 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 16 Feb 2022 10:13:14 +0800 Subject: Re: [PATCH v2] mm: clean up hwpoison page cache page in fault path To: Oscar Salvador , Rik van Riel CC: , , , Andrew Morton , Mel Gorman , Johannes Weiner , Matthew Wilcox References: <20220212213740.423efcea@imladris.surriel.com> From: Miaohe Lin Message-ID: Date: Wed, 16 Feb 2022 10:13:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/2/15 20:51, Oscar Salvador wrote: > On Sat, Feb 12, 2022 at 09:37:40PM -0500, Rik van Riel wrote: >> Sometimes the page offlining code can leave behind a hwpoisoned clean >> page cache page. This can lead to programs being killed over and over >> and over again as they fault in the hwpoisoned page, get killed, and >> then get re-spawned by whatever wanted to run them. > > Hi Rik, > > Do you know how that exactly happens? We should not be really leaving > anything behind, and soft-offline (not hard) code works with the premise > of only poisoning a page in case it was contained, so I am wondering > what is going on here. > > In-use pagecache pages are migrated away, and the actual page is > contained, and for clean ones, we already do the invalidate_inode_page() > and then contain it in case we succeed. > IIUC, this could not happen when soft-offlining a pagecache page. They're either invalidated or migrated away and then we set PageHWPoison. I think this may happen on a clean pagecache page when it's isolated. So it's !PageLRU. And identify_page_state treats it as me_unknown because it's non reserved, slab, swapcache and so on ...(see error_states for details). Or am I miss anything? Thanks. > One scenario I can imagine this can happen is if by the time we call > page_handle_poison(), someone has taken another refcount on the page, > and the put_page() does not really free it, but I am not sure that > can happen. >