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Shutemov" , Matthew Wilcox Cc: Johannes Weiner , Linux-MM , "linux-kernel@vger.kernel.org" , Hugh Dickins References: <20200709155002.GF12769@casper.infradead.org> <20200709160750.utl46xvavceuvnom@box> <441ebbeb-0408-e22e-20f4-1be571c4a18e@nextfour.com> From: =?UTF-8?Q?Mika_Penttil=c3=a4?= X-Pep-Version: 2.0 Message-ID: Date: Fri, 10 Jul 2020 10:22:09 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------FA6F8C6E10F6277D639547ED" Content-Language: en-US X-ClientProxiedBy: HE1PR07CA0020.eurprd07.prod.outlook.com (2603:10a6:7:67::30) To HE1PR0302MB2682.eurprd03.prod.outlook.com (2603:10a6:3:f5::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.10.10.126] (194.157.170.35) by HE1PR07CA0020.eurprd07.prod.outlook.com (2603:10a6:7:67::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3174.13 via Frontend Transport; Fri, 10 Jul 2020 07:22:10 +0000 X-Pep-Version: 2.0 X-Originating-IP: [194.157.170.35] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: b557bb1b-b44c-42c2-c8bb-08d824a1f589 X-MS-TrafficTypeDiagnostic: HE1PR03MB3113: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: mkgB672BYKjuKjrTzihV1KZyJTfX7ytza3uBvhkwEdxUZQ86l/Hx13Tqcy9nhUHMrzjk6by2t0cjdetUVl3Hwx5JQa5TY8HhM2L2kwsxWNIS1/i4blK6bLIkMIEg1EzPzzr1m4brQHd8+or3vp/Dv11YB4TQfDYTNG6/iZne7rhv/nqjmUffAF8E6JK/j3rOMu08e1jVatkl85gbkJpQda3Tm8Kgz3JFAL4POKNfvnnRrvju3+oS8TCRhQDXUKIBpVpFU/gFchRGpfiae7lWqa8O3iItOwTnMbupRojkr3MW9886ObCA1b+jqU37hznpz3XO26crkyX4DhtWfZvoz12PEDOYdgURBif8n6ltdkJfgJBXx1C/puAhPBNALeSFvlhwg+XIj7k7oJk1GImH4g== X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:HE1PR0302MB2682.eurprd03.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(396003)(39830400003)(376002)(136003)(366004)(346002)(86362001)(8676002)(31696002)(83380400001)(36756003)(5660300002)(235185007)(2616005)(956004)(31686004)(66556008)(66476007)(66616009)(508600001)(2906002)(16526019)(4326008)(186003)(316002)(6486002)(26005)(110136005)(52116002)(54906003)(33964004)(66946007)(21480400003)(16576012)(8936002)(14583001)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: yScUlnFsTWkZkpVwixhMDcEBzyFgvDYI+d7VJ1EJRe7eBM8gI6h67TPfHz6u1am0avc32BJ3p6AgAmW77U+yHjw0xuyiuRwyd/IkZV954HFJie065MS3zD2aKOreN56KIqs6uFlcxCQfzs0Tng6jd+RR/Ki9aFpvrNgd4hvrovM2UU9IXmPsj6tmDbDbzjdD0NOCsJ9QA7v+v4n8t+tWU0Q6SEne+i2cDqqC6/ZXW6UqVcyb4JhgT/957UGp6Xlp3EUDKNGLI3A/+WQ+SwY5nRYZH2CLLkXx9DtQNXN4ra+M4qrOVuy4rSSlYMQ9JDWbi2SjNv/nj4FwUUEU0ZEGkbvrdoGI2MdAZ4amrh3C+LGCBTDAeh0ng9gPHKhGY8g+Ly/DJXqkmr5B11F5zfsWb4XfoHNFNVOJGajrt0ytO5b6EqfBsYiClhCaOxIBHnFW2aFe/EixfTUAH1nYgIVShfifo0NBs+ARE5un4FkSmlQ= X-OriginatorOrg: nextfour.com X-MS-Exchange-CrossTenant-Network-Message-Id: b557bb1b-b44c-42c2-c8bb-08d824a1f589 X-MS-Exchange-CrossTenant-AuthSource: HE1PR0302MB2682.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jul 2020 07:22:10.3016 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 972e95c2-9290-4a02-8705-4014700ea294 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: gRnCLz2CM3rDB6wPTZNUyHOyxcBch96h2d5xWEhb1LiKysKETmuNZ7MugUwIPWODzJAJcH+yjk0ActTnpdx346z41LwU0sY4S2pRsz6bKEc= X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR03MB3113 X-Rspamd-Queue-Id: E28F730001F024FC X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: --------------FA6F8C6E10F6277D639547ED Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 10.7.2020 10.00, Alex Shi wrote: > > =E5=9C=A8 2020/7/10 =E4=B8=8B=E5=8D=881:28, Mika Penttil=C3=A4 =E5=86=99= =E9=81=93: >>> Thanks a lot for quick reply! >>> What I am confusing is the call chain: __iommu_dma_alloc_pages() >>> to split_huge_page(), in the func, splited page, >>> page =3D alloc_pages_node(nid, alloc_flags, order); >>> And if the pages were added into lru, they maybe reclaimed and lost, >>> that would be a panic bug. But in fact, this never happened for long ti= me. >>> Also I put a BUG() at the line, it's nevre triggered in ltp, and run_vm= tests >> In=C2=A0 __iommu_dma_alloc_pages, after split_huge_page(),=C2=A0 who is = taking a >> reference on tail pages? Seems tail pages are freed and the function >> errornously returns them in pages[] array for use? >> > Why you say so? It looks like the tail page returned and be used > pages =3D __iommu_dma_alloc_pages() in iommu_dma_alloc_remap() > and still on node's lru. Is this right? > > thanks! IMHO they are new pages coming from alloc_pages_node() so they are not on lru. And split_huge_page() frees not pinned tail pages again to page allocator. 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