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Fri, 26 Jul 2019 21:19:54 +0000 From: Song Liu To: Oleg Nesterov CC: lkml , Linux-MM , "Andrew Morton" , "matthew.wilcox@oracle.com" , "kirill.shutemov@linux.intel.com" , "peterz@infradead.org" , "rostedt@goodmis.org" , "Kernel Team" , "william.kucharski@oracle.com" Subject: Re: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Thread-Topic: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Thread-Index: AQHVQfsnepoAlMhPK0qmuIU0gpphb6bZpE2AgAB5kgCAAOAOAIAAqHSAgADyToCAANMVgA== Date: Fri, 26 Jul 2019 21:19:54 +0000 Message-ID: <4398BBD5-31AB-4342-9572-32763B016175@fb.com> References: <20190724083600.832091-1-songliubraving@fb.com> <20190724083600.832091-3-songliubraving@fb.com> <20190724113711.GE21599@redhat.com> <20190725081414.GB4707@redhat.com> <20190726084423.GA16112@redhat.com> In-Reply-To: <20190726084423.GA16112@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:c090:180::1:bb04] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: bb4ea2bf-d7ea-4df1-4355-08d7120f00c9 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1902; 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charset="us-ascii" Content-ID: <8092EDAF1C73394291E86563B64E33D3@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: bb4ea2bf-d7ea-4df1-4355-08d7120f00c9 X-MS-Exchange-CrossTenant-originalarrivaltime: 26 Jul 2019 21:19:54.0952 (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: MWHPR15MB1902 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-26_15:,, 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=710 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907260241 X-FB-Internal: deliver 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 Jul 26, 2019, at 1:44 AM, Oleg Nesterov wrote: >=20 > On 07/25, Song Liu wrote: >>=20 >> I guess I know the case now. We can probably avoid this with an simp=10l= e=20 >> check for old_page =3D=3D new_page? >=20 > better yet, I think we can check PageAnon(old_page) and avoid the unneces= sary > __replace_page() in this case. See the patch below. I added PageAnon(old_page) check in v9 of the patch.=20 >=20 > Anyway, why __replace_page() needs to lock both pages? This doesn't look = nice > even if it were correct. I think it can do lock_page(old_page) later. >=20 Agreed. I have changed the v9 to only unmap old_page. So it should be clean= er.=20 Thanks again for these good suggestions, Song=