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dkim=none (message not signed) header.d=none;amazon.com; dmarc=none action=none header.from=oracle.com; Received: from BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) by BYAPR10MB3253.namprd10.prod.outlook.com (2603:10b6:a03:154::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3912.30; Wed, 10 Mar 2021 18:56:12 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::980e:61ba:57d2:47ee]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::980e:61ba:57d2:47ee%7]) with mapi id 15.20.3912.029; Wed, 10 Mar 2021 18:56:12 +0000 Subject: Re: [PATCH v18 4/9] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page To: Michal Hocko , Muchun Song Cc: corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, osalvador@suse.de, song.bao.hua@hisilicon.com, david@redhat.com, naoya.horiguchi@nec.com, joao.m.martins@oracle.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Chen Huang , Bodeddula Balasubramaniam References: <20210308102807.59745-1-songmuchun@bytedance.com> <20210308102807.59745-5-songmuchun@bytedance.com> From: Mike Kravetz Message-ID: Date: Wed, 10 Mar 2021 10:56:08 -0800 User-Agent: Mozilla/5.0 (X11; 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Yes, the issue of calling put_page for hugetlb pages from any context still needs work. IMO, that is outside the scope of this series. We already have code in this path which blocks/sleeps. Making HUGETLB depend on PREEMPT_COUNT is too restrictive. IIUC, PREEMPT_COUNT will only be enabled if we enable: PREEMPT "Preemptible Kernel (Low-Latency Desktop)" PREEMPT_RT "Fully Preemptible Kernel (Real-Time)" or, other 'debug' options. These are not enabled in 'more common' kernels. Of course, we do not want to disable HUGETLB in common configurations. I'll put together a separate patch where we can discuss the merits of making the change from !in_task to in_atomic, and what work remains in this put_page area. -- Mike Kravetz