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 AF3AEC433F5 for ; Thu, 17 Mar 2022 01:58:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3EC0A6B0071; Wed, 16 Mar 2022 21:58:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 399C38D0002; Wed, 16 Mar 2022 21:58:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 261EE8D0001; Wed, 16 Mar 2022 21:58:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 161F66B0071 for ; Wed, 16 Mar 2022 21:58:00 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id B597160C4D for ; Thu, 17 Mar 2022 01:57:59 +0000 (UTC) X-FDA: 79252217478.02.67BBD1B Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf28.hostedemail.com (Postfix) with ESMTP id 7C19BC0013 for ; Thu, 17 Mar 2022 01:57:58 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KJqsh64wnzcb5l; Thu, 17 Mar 2022 09:52:56 +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; Thu, 17 Mar 2022 09:57:55 +0800 Subject: Re: [PATCH] hugetlb: do not demote poisoned hugetlb pages To: Mike Kravetz , , CC: HORIGUCHI NAOYA , Oscar Salvador , Michal Hocko , Andrew Morton , References: <20220307215707.50916-1-mike.kravetz@oracle.com> <6ba788b3-901e-d740-2575-bc652461187b@huawei.com> <8b40c33f-1bdf-2cda-5948-cf433302514e@oracle.com> From: Miaohe Lin Message-ID: Date: Thu, 17 Mar 2022 09:57:55 +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: <8b40c33f-1bdf-2cda-5948-cf433302514e@oracle.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 7C19BC0013 X-Rspam-User: Authentication-Results: imf28.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf28.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: towei4wg6etgyq6pbup8hh8qzidkp76x X-Rspamd-Server: rspam04 X-HE-Tag: 1647482278-449566 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: On 2022/3/17 6:31, Mike Kravetz wrote: > On 3/8/22 05:43, Miaohe Lin wrote: >> On 2022/3/8 5:57, Mike Kravetz wrote: >>> It is possible for poisoned hugetlb pages to reside on the free lists. >>> The huge page allocation routines which dequeue entries from the free >>> lists make a point of avoiding poisoned pages. There is no such check >>> and avoidance in the demote code path. >>> >>> If a hugetlb page on the is on a free list, poison will only be set in >>> the head page rather then the page with the actual error. If such a >>> page is demoted, then the poison flag may follow the wrong page. A page >>> without error could have poison set, and a page with poison could not >>> have the flag set. >>> >>> Check for poison before attempting to demote a hugetlb page. Also, >>> return -EBUSY to the caller if only poisoned pages are on the free list. >>> >>> Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support") >>> Signed-off-by: Mike Kravetz >>> Cc: >>> --- >>> mm/hugetlb.c | 17 ++++++++++------- >>> 1 file changed, 10 insertions(+), 7 deletions(-) >>> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>> index b34f50156f7e..f8ca7cca3c1a 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -3475,7 +3475,6 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) >>> { >>> int nr_nodes, node; >>> struct page *page; >>> - int rc = 0; >>> >>> lockdep_assert_held(&hugetlb_lock); >>> >>> @@ -3486,15 +3485,19 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) >>> } >>> >>> for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) { >>> - if (!list_empty(&h->hugepage_freelists[node])) { >>> - page = list_entry(h->hugepage_freelists[node].next, >>> - struct page, lru); >>> - rc = demote_free_huge_page(h, page); >>> - break; >>> + list_for_each_entry(page, &h->hugepage_freelists[node], lru) { >>> + if (PageHWPoison(page)) >>> + continue; >>> + >>> + return demote_free_huge_page(h, page); >> >> It seems this patch is not ideal. Memory failure can hit the hugetlb page anytime without >> holding the hugetlb_lock. So the page might become HWPoison just after the check. But this >> patch should have handled the common case. Many thanks for your work. :) >> > > Correct, this patch handles the common case of not demoting a hugetlb > page if HWPoison is set. This is similar to code in the dequeue path > used when allocating a huge page for allocation use. > > As you point out, work still needs to be done to better coordinate > memory failure with demote as well as huge page freeing. As you know > Naoya is working on this now. It is unclear if that work will be limited > to memory error handling code, or if greater coordination with hugetlb > code will be required. > > Unless you have objections, I believe this patch should move forward and > be backported to stable trees. If we determine that more coordination > between memory error and hugetlb code is needed, that can be added later. I think this patch is good enough to move forward and be backported to stable trees. Many thanks. :) >