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Thu, 20 Jun 2019 02:10:16 +0000 From: Song Liu To: Rik van Riel CC: "linux-mm@kvack.org" , "matthew.wilcox@oracle.com" , "kirill.shutemov@linux.intel.com" , Kernel Team , "william.kucharski@oracle.com" , "akpm@linux-foundation.org" Subject: Re: [PATCH v3 6/6] mm,thp: handle writes to file with THP in pagecache Thread-Topic: [PATCH v3 6/6] mm,thp: handle writes to file with THP in pagecache Thread-Index: AQHVJmezv99wdCcaVEmWmrPzjMSHT6ajxTGAgAAImQA= Date: Thu, 20 Jun 2019 02:10:16 +0000 Message-ID: References: <20190619062424.3486524-1-songliubraving@fb.com> <20190619062424.3486524-7-songliubraving@fb.com> <9ec5787861152deb1c6c6365b593343b3aef18d4.camel@fb.com> In-Reply-To: <9ec5787861152deb1c6c6365b593343b3aef18d4.camel@fb.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::1:8b5f] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 12789224-1134-45c0-68d5-08d6f5247013 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1550; 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charset="us-ascii" Content-ID: <318691919763C544863EFDAA3EBCA34C@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 12789224-1134-45c0-68d5-08d6f5247013 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Jun 2019 02:10:16.6270 (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: MWHPR15MB1550 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-20_01:,, 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=736 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906200015 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 Jun 19, 2019, at 6:39 PM, Rik van Riel wrote: >=20 > On Tue, 2019-06-18 at 23:24 -0700, Song Liu wrote: >=20 >> index 8563339041f6..bab8d9eef46c 100644 >> --- a/mm/truncate.c >> +++ b/mm/truncate.c >> @@ -790,7 +790,11 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages2); >> void truncate_pagecache(struct inode *inode, loff_t newsize) >> { >> struct address_space *mapping =3D inode->i_mapping; >> - loff_t holebegin =3D round_up(newsize, PAGE_SIZE); >> + loff_t holebegin; >> + >> + /* if non-shmem file has thp, truncate the whole file */ >> + if (filemap_nr_thps(mapping)) >> + newsize =3D 0; >>=20 >=20 > I don't get it. Sometimes truncate is used to > increase the size of a file, or to change it > to a non-zero size. >=20 > Won't forcing the newsize to zero break applications, > when the file is truncated to a different size than > they expect? This is not truncate the file. It only drops page cache.=20 truncate_setsize() will still set correct size. I don't=20 think this breaks anything.=20 We can probably make it smarter and only drop the clean huge pages (dirty page should not exist).=20 Thanks, Song