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dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=oracle.com; Received: from BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) by BYAPR10MB3494.namprd10.prod.outlook.com (2603:10b6:a03:11d::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4195.22; Fri, 4 Jun 2021 23:55:43 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::4407:2ff6:c0a:5d90]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::4407:2ff6:c0a:5d90%9]) with mapi id 15.20.4195.025; Fri, 4 Jun 2021 23:55:43 +0000 Subject: Re: [PATCH v6 1/2] mm,hwpoison: fix race with hugetlb page allocation To: Naoya Horiguchi , Oscar Salvador , Muchun Song , linux-mm@kvack.org Cc: Andrew Morton , Michal Hocko , Tony Luck , Naoya Horiguchi , linux-kernel@vger.kernel.org References: <20210603233632.2964832-1-nao.horiguchi@gmail.com> <20210603233632.2964832-2-nao.horiguchi@gmail.com> From: Mike Kravetz Message-ID: <69922ccb-9ab9-33a6-4aa6-ea47431d60a7@oracle.com> Date: Fri, 4 Jun 2021 16:55:40 -0700 User-Agent: Mozilla/5.0 (X11; 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Checking hugetlb-specific flags > under hugetlb_lock makes sure that the hugetlb page is not transitive. > It's notable that another new function, HWPoisonHandlable(), is helpful > to prevent a race against other transitive page states (like a generic > compound page just before PageHuge becomes true). Thanks! I believe this is good enough to prevent the race. Since access to the page is not synchronized in any way, it would still be "theoretically possible" to race. For example, CPU0: CPU1: HWPoisonHandlable true page freed to buddy page allocated from buddy page added to hugetlb pool alloc_surplus_huge_page But, this is very Very VERY unlikely to ever happen. > > Fixes: ead07f6a867b ("mm/memory-failure: introduce get_hwpoison_page() for consistent refcount handling") > Signed-off-by: Naoya Horiguchi > Reported-by: Muchun Song > Cc: stable@vger.kernel.org # 5.12+ > --- > ChangeLog v6: > - defined HWPoisonHandlable(), > - updated comment and patch description. > --- > include/linux/hugetlb.h | 6 ++++++ > mm/hugetlb.c | 15 +++++++++++++++ > mm/memory-failure.c | 29 +++++++++++++++++++++++++++-- > 3 files changed, 48 insertions(+), 2 deletions(-) Acked-by: Mike Kravetz -- Mike Kravetz