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Shutemov" , Peter Zijlstra , Steven Rostedt , Kernel Team , William Kucharski Subject: Re: [PATCH v7 2/4] uprobe: use original page when all uprobes are removed Thread-Topic: [PATCH v7 2/4] uprobe: use original page when all uprobes are removed Thread-Index: AQHVK7E/mgao02pfukuBDym1pWgYbqbL65wAgA2vQ4A= Date: Wed, 24 Jul 2019 08:23:53 +0000 Message-ID: References: <20190625235325.2096441-1-songliubraving@fb.com> <20190625235325.2096441-3-songliubraving@fb.com> <20190715152513.GD1222@redhat.com> In-Reply-To: <20190715152513.GD1222@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::1:87bf] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: c2dfda01-d6db-4416-421c-08d7101043c7 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1886; x-ms-traffictypediagnostic: MWHPR15MB1886: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8273; x-forefront-prvs: 0108A997B2 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(346002)(39860400002)(366004)(136003)(376002)(396003)(199004)(189003)(8936002)(71190400001)(66946007)(71200400001)(53546011)(46003)(86362001)(316002)(76116006)(6506007)(186003)(66556008)(54906003)(76176011)(57306001)(11346002)(68736007)(478600001)(66476007)(486006)(64756008)(6116002)(102836004)(2616005)(476003)(33656002)(50226002)(229853002)(14454004)(446003)(6246003)(305945005)(7736002)(6512007)(25786009)(6916009)(53936002)(81166006)(256004)(66446008)(4326008)(6486002)(36756003)(4744005)(8676002)(5660300002)(6436002)(99286004)(81156014)(2906002);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1886;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: DM9bz7qTmOMV7TTyawcNnCXSKtlWkjAHLvxeTjdnIvUz5+J/Ydhtvmsw0fKLU9TmiY66u39Zh0PNgij00rfJRTwgDsHLCvhJL2w1ynmBsVm28CE7Qgx5VmatwkQDcc9gQLOZl6PTk6Z89x7DhIDW4sHLpGXLjO5CUo52dfiTx9V2ubEEVPVaI9Yc4a6Zluetnh9aQ4ZWP7qd9ahg+tHEM5HuHEyDunooY82+SBKBc+6S1xS83idvRG+mg63mFnGGAAIHMxWlzBh2xpBpsyaGQ3qbEw+/cgHEr756k6MVMPdtITwgpj1HVLI/POkKMgPQYE+jApcd669je/S4K6yppwF5ky59n3rh3aTCmZpm+SI/r/p0QaPuC9q/8a9Nz1LUNBaTLQsNwG9LrWTRloLTmO2Qc4Vrs79yOPIQcxOIRJo= Content-Type: text/plain; charset="us-ascii" Content-ID: <8F2491EDA647EE46934F82283A5D9F9B@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: c2dfda01-d6db-4416-421c-08d7101043c7 X-MS-Exchange-CrossTenant-originalarrivaltime: 24 Jul 2019 08:23:53.7726 (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: MWHPR15MB1886 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-24_03:,, 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=836 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907240094 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jul 15, 2019, at 8:25 AM, Oleg Nesterov wrote: >=20 > On 06/25, Song Liu wrote: >>=20 >> This patch allows uprobe to use original page when possible (all uprobes >> on the page are already removed). >=20 > I can't review. I do not understand vm enough. >=20 >> + if (!is_register) { >> + struct page *orig_page; >> + pgoff_t index; >> + >> + index =3D vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT; >> + orig_page =3D find_get_page(vma->vm_file->f_inode->i_mapping, >> + index); >> + >> + if (orig_page) { >> + if (pages_identical(new_page, orig_page)) { >=20 > Shouldn't we at least check PageUptodate? For page cache, we only do ClearPageUptodate() on read failures, so=20 this should be really rare case. But I guess we can check anyway.=20 >=20 > and I am a bit surprised there is no simple way to unmap the old page > in this case...=20 The easiest way I have found requires flush_cache_page() plus a few mmu_notifier calls around it. I think current solution is better than that, as it saves a page fault.=20 Thanks, Song