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Petersen" , "linux-fsdevel@vger.kernel.org" , Johannes Thumshirn , Shinichiro Kawasaki Subject: Re: [PATCH v2 3/3] zonefs: fix synchronous write to sequential zone files Thread-Topic: [PATCH v2 3/3] zonefs: fix synchronous write to sequential zone files Thread-Index: AQHXMzIUD8ZVvai2c0OhPeRaKpo++w== Date: Tue, 20 Apr 2021 01:35:21 +0000 Message-ID: References: <20210417023323.852530-1-damien.lemoal@wdc.com> <20210417023323.852530-4-damien.lemoal@wdc.com> <20210419064529.GA19041@lst.de> <9a4d5090-1a70-129a-72f7-3699db0038a1@interlog.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: interlog.com; dkim=none (message not signed) header.d=none;interlog.com; dmarc=none action=none header.from=wdc.com; x-originating-ip: [2400:2411:43c0:6000:b085:266a:414b:c56a] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: bdc245fa-646d-4c17-52df-08d9039c9051 x-ms-traffictypediagnostic: MN2PR04MB7008: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:4502; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BL0PR04MB6514.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: bdc245fa-646d-4c17-52df-08d9039c9051 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Apr 2021 01:35:21.9590 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: VdwDmpU0srsXULzQJMEHRDRmuJMCLSYoLrXQ+/nBsUq7nAwfGOxV5lJwf97nUnc7QAsyYSaCvLrR59Pmi0bz5g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR04MB7008 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2021/04/20 10:20, Douglas Gilbert wrote:=0A= > On 2021-04-19 2:45 a.m., Christoph Hellwig wrote:=0A= >> On Sat, Apr 17, 2021 at 11:33:23AM +0900, Damien Le Moal wrote:=0A= >>> Synchronous writes to sequential zone files cannot use zone append=0A= >>> operations if the underlying zoned device queue limit=0A= >>> max_zone_append_sectors is 0, indicating that the device does not=0A= >>> support this operation. In this case, fall back to using regular write= =0A= >>> operations.=0A= >>=0A= >> Zone append is a mandatory feature of the zoned device API.=0A= > =0A= > So a hack required for ZNS and not needed by ZBC and ZAC becomes=0A= > a "mandatory feature" in a Linux API. Like many hacks, that one might=0A= > come back to bite you :-)=0A= =0A= Zone append is not a hack in ZNS. It is a write interface that fits very we= ll=0A= with the multi-queue nature of NVMe. The "hack" is the emulation in scsi.= =0A= =0A= We decided on having this mandatory for zoned devices (all types) to make s= ure=0A= that file systems do not have to implement different IO paths for sequentia= l=0A= writing to zones. Zone append does simplify a lot of things and allows to g= et=0A= the best performance from ZNS drives. Zone write locking/serialization of w= rites=0A= per zones using regular writes is much harder to implement, make a mess of = the=0A= file system code, and would kill write performance on ZNS.=0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=