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Thu, 1 Aug 2019 17:11:28 +0000 Received: from MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::d4fc:70c0:79a5:f41b]) by MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::d4fc:70c0:79a5:f41b%2]) with mapi id 15.20.2115.005; Thu, 1 Aug 2019 17:11:28 +0000 From: Song Liu To: Oleg Nesterov CC: lkml , Linux-MM , Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , Kernel Team , "William Kucharski" , "srikar@linux.vnet.ibm.com" Subject: Re: [PATCH v2 1/2] khugepaged: enable collapse pmd for pte-mapped THP Thread-Topic: [PATCH v2 1/2] khugepaged: enable collapse pmd for pte-mapped THP Thread-Index: AQHVR86KvCEU4VHLnkGVG5f001755abmPe4AgABKxAA= Date: Thu, 1 Aug 2019 17:11:28 +0000 Message-ID: <619E9EC6-0B6A-4C30-8BA7-D2CA83FFC4E7@fb.com> References: <20190731183331.2565608-1-songliubraving@fb.com> <20190731183331.2565608-2-songliubraving@fb.com> <20190801124351.GA31538@redhat.com> In-Reply-To: <20190801124351.GA31538@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3445.104.11) x-originating-ip: [2620:10d:c090:200::2:33d7] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 2655aed1-83bd-4f83-21be-08d716a34ad8 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1904; x-ms-traffictypediagnostic: MWHPR15MB1904: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:4125; x-forefront-prvs: 01165471DB x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(39860400002)(136003)(346002)(376002)(396003)(366004)(199004)(189003)(14454004)(7736002)(86362001)(76176011)(99286004)(6916009)(186003)(6436002)(71200400001)(6506007)(66476007)(68736007)(316002)(53936002)(66946007)(53546011)(76116006)(66556008)(6512007)(305945005)(14444005)(64756008)(486006)(256004)(102836004)(476003)(229853002)(5660300002)(11346002)(36756003)(446003)(2616005)(6486002)(54906003)(71190400001)(46003)(6246003)(8936002)(81166006)(8676002)(33656002)(66446008)(6116002)(4326008)(25786009)(2906002)(50226002)(57306001)(478600001)(81156014);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1904;H:MWHPR15MB1165.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: XNHVRJUxyTa4DAesDGRL/nYDMME3cJk0vLkmWPlK+Q3WskdobNHgq0/ThLcsc8Hs6f1YE7In75eeaYFYw6ZkIUBSJJ5xqrvbKQ5qF38wr4OkZAkIz0rn7OaSq4FDe1enHCaMfssRq8tSqPy47WaFCqovR3AYKYaEF7c6wzZme+fKjPDL+Efp2mrhr5N4xoD4eI3WA4SHiSBPp+RxvnYINMDRrAscJ7kQVaaHnRupGTV2z+vRNwx6/KFQ9tz12MuifjIJXbD16xRlnjkYKGom7q9O/Dt71EQZoFZpJniIEmVp0uHWn4+dtvTILbl4QmhwzSIZfewDcJh28o+f7bQhCSAJ5xnsK44j/SB/1ZzCDPEctBnbyjrcjy7DmI8utv7Dr/cp+sm1a4Mx9+hDT3+u0mn7c2VtpX2GRZrZFHyrOUM= Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 2655aed1-83bd-4f83-21be-08d716a34ad8 X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Aug 2019 17:11:28.5541 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: songliubraving@fb.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1904 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-01_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=998 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908010179 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Aug 1, 2019, at 5:43 AM, Oleg Nesterov wrote: >=20 > On 07/31, Song Liu wrote: >>=20 >> +void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long haddr) >> +{ >> + struct vm_area_struct *vma =3D find_vma(mm, haddr); >> + pmd_t *pmd =3D mm_find_pmd(mm, haddr); >> + struct page *hpage =3D NULL; >> + unsigned long addr; >> + spinlock_t *ptl; >> + int count =3D 0; >> + pmd_t _pmd; >> + int i; >> + >> + VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); >> + >> + if (!vma || !pmd || pmd_trans_huge(*pmd)) > ^^^^^^^^^^^^^^^^^^^^ >=20 > mm_find_pmd() returns NULL if pmd_trans_huge() Good catch! I will simplify this one in v3.=20 >=20 >> + /* step 1: check all mapped PTEs are to the right huge page */ >> + for (i =3D 0, addr =3D haddr; i < HPAGE_PMD_NR; i++, addr +=3D PAGE_SI= ZE) { >> + pte_t *pte =3D pte_offset_map(pmd, addr); >> + struct page *page; >> + >> + if (pte_none(*pte)) >> + continue; >> + >> + page =3D vm_normal_page(vma, addr, *pte); >> + >> + if (!PageCompound(page)) >> + return; >> + >> + if (!hpage) { >> + hpage =3D compound_head(page); >> + if (hpage->mapping !=3D vma->vm_file->f_mapping) >=20 > Hmm. But how can we know this is still the same vma ? >=20 > If nothing else, why vma->vm_file can't be NULL? Good point. We should confirm vma->vm_file is not NULL.=20 Thanks, Song