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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688977954; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/mC7ivaU1i57YS154Z2VEikHOnPJL2MIKo+CwsFoBn8=; b=kDJ25lazmxlnOAaqJJEJH75uiJCOB+fRsxRN+i5JF9GEiWZ1FEGyC8P7ijkiUbVZLl66Gi toW+A+Ap1WAPjzbA752fk/z9xn2k5GO3Z6s6lxSW+6VwO58a3ygtVo7Gx5368vXXXhfAWZ 5bf3KgYFaUtV/bPqD0Yg1lvwiuv06qY= Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Qzy0X2LTXz1FDnC; Mon, 10 Jul 2023 16:31:56 +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; Mon, 10 Jul 2023 16:32:27 +0800 Subject: Re: [PATCH 8/8] mm: memory-failure: fix race window when trying to get hugetlb folio To: Naoya Horiguchi CC: , , , References: <20230708085744.3599311-1-linmiaohe@huawei.com> <20230708085744.3599311-9-linmiaohe@huawei.com> <20230710075812.GH1686200@ik1-406-35019.vs.sakura.ne.jp> From: Miaohe Lin Message-ID: <74acb109-76cc-3990-c770-8330e343ef54@huawei.com> Date: Mon, 10 Jul 2023 16:32:27 +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: <20230710075812.GH1686200@ik1-406-35019.vs.sakura.ne.jp> 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 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 67E4E140015 X-Stat-Signature: 8gf7tuiqqydpy5k94qb31jqm1i1w1mtk X-Rspam-User: X-HE-Tag: 1688977953-268698 X-HE-Meta: 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 TIdUTZiT QUV7EZ8t6hlsRoZRQpT5htkjABSlB/oFmH8trknKnWODqTJrsoAoR6bbolhhAA4/DAD+bMXVxkZocaZrhIGpy5ZiYOwbeQniapa3mHP2gQjnr327GKenpxBfcgNw2cI7WpE6bZYJcUjesHqkPHLn0UPpMTdwQ+LFkf0L3Ihg+Y1sKRTQ= 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 2023/7/10 15:58, Naoya Horiguchi wrote: > On Sat, Jul 08, 2023 at 04:57:44PM +0800, Miaohe Lin wrote: >> page_folio() is fetched before calling get_hwpoison_hugetlb_folio() >> without hugetlb_lock being held. So hugetlb page could be demoted >> before get_hwpoison_hugetlb_folio() holding hugetlb_lock but after >> page_folio() is fetched. So get_hwpoison_hugetlb_folio() will hold >> unexpected extra refcnt of hugetlb folio while leaving demoted page >> un-refcnted. > > Very nice, thank you for finding the issue. > >> >> Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation") >> Signed-off-by: Miaohe Lin >> --- >> mm/memory-failure.c | 18 ++++++++++++++---- >> 1 file changed, 14 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 76d88d27cdbe..066bf57f2d22 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -1388,8 +1388,14 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags) >> bool hugetlb = false; >> >> ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false); >> - if (hugetlb) >> - return ret; >> + if (hugetlb) { >> + if (folio == page_folio(page)) >> + return ret; > > Some short comment about the race against demotion here is helpful. Does the below comment makes sense to you? " Make sure hugetlb demotion did not happen from under us. " > > Anyway, the patch looks good to me. > > Acked-by: Naoya Horiguchi Many thanks for your review and comment, Naoya.