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 D7E67C001B0 for ; Sat, 8 Jul 2023 02:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232805AbjGHC5H (ORCPT ); Fri, 7 Jul 2023 22:57:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229699AbjGHC5F (ORCPT ); Fri, 7 Jul 2023 22:57:05 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 567181999 for ; Fri, 7 Jul 2023 19:57:04 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4QyZcQ2khxzPk16; Sat, 8 Jul 2023 10:54:46 +0800 (CST) Received: from [10.174.151.185] (10.174.151.185) 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 15.1.2507.27; Sat, 8 Jul 2023 10:57:01 +0800 Subject: Re: [PATCH v3 2/4] mm/hwpoison: check if a subpage of a hugetlb folio is raw HWPOISON To: Jiaqi Yan , , , CC: , , , , , , References: <20230707201904.953262-1-jiaqiyan@google.com> <20230707201904.953262-3-jiaqiyan@google.com> From: Miaohe Lin Message-ID: <6682284d-7ad3-9b59-687d-899f4d08d911@huawei.com> Date: Sat, 8 Jul 2023 10:57:00 +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: <20230707201904.953262-3-jiaqiyan@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.151.185] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) 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 2023/7/8 4:19, Jiaqi Yan wrote: > Add the functionality, is_raw_hwp_subpage, to tell if a subpage of a > hugetlb folio is a raw HWPOISON page. This functionality relies on > RawHwpUnreliable to be not set; otherwise hugepage's raw HWPOISON list > becomes meaningless. > > is_raw_hwp_subpage needs to hold hugetlb_lock in order to synchronize > with __get_huge_page_for_hwpoison, who iterates and inserts an entry to > raw_hwp_list. llist itself doesn't ensure insertion is synchornized with > the iterating used by __is_raw_hwp_list. Caller can minimize the > overhead of lock cycles by first checking if folio / head page's > HWPOISON flag is set. > > Exports this functionality to be immediately used in the read operation > for hugetlbfs. > > Reviewed-by: Mike Kravetz > Reviewed-by: Naoya Horiguchi > Signed-off-by: Jiaqi Yan > --- > include/linux/hugetlb.h | 19 +++++++++++++++++++ > include/linux/mm.h | 7 +++++++ > mm/hugetlb.c | 10 ++++++++++ > mm/memory-failure.c | 34 ++++++++++++++++++++++++---------- > 4 files changed, 60 insertions(+), 10 deletions(-) > ... > -static inline struct llist_head *raw_hwp_list_head(struct folio *folio) > +bool __is_raw_hwp_subpage(struct folio *folio, struct page *subpage) > { > - return (struct llist_head *)&folio->_hugetlb_hwpoison; > + struct llist_head *raw_hwp_head; > + struct raw_hwp_page *p, *tmp; > + bool ret = false; > + > + if (!folio_test_hwpoison(folio)) > + return false; > + > + /* > + * When RawHwpUnreliable is set, kernel lost track of which subpages > + * are HWPOISON. So return as if ALL subpages are HWPOISONed. > + */ > + if (folio_test_hugetlb_raw_hwp_unreliable(folio)) > + return true; > + > + raw_hwp_head = raw_hwp_list_head(folio); > + llist_for_each_entry_safe(p, tmp, raw_hwp_head->first, node) { Since we don't free the raw_hwp_list, does llist_for_each_entry works same as llist_for_each_entry_safe? > + if (subpage == p->page) { > + ret = true; > + break; > + } > + } > + > + return ret; > } It seems there's a race between __is_raw_hwp_subpage and unpoison_memory: unpoison_memory __is_raw_hwp_subpage if (!folio_test_hwpoison(folio)) -- hwpoison is set folio_free_raw_hwp llist_for_each_entry_safe raw_hwp_list llist_del_all .. folio_test_clear_hwpoison But __is_raw_hwp_subpage is used in hugetlbfs, unpoison_memory couldn't reach here because there's a folio_mapping == NULL check before folio_free_raw_hwp. Anyway, this patch looks good to me. Reviewed-by: Miaohe Lin Thanks.