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Mon, 1 Mar 2021 13:04:55 +0000 From: Damien Le Moal To: Guido Trentalancia , "linux-scsi@vger.kernel.org" Subject: Re: [PATCH RESEND v2] scsi: ignore Synchronize Cache command failures to keep using drives not supporting it Thread-Topic: [PATCH RESEND v2] scsi: ignore Synchronize Cache command failures to keep using drives not supporting it Thread-Index: AQHXDbGOoQvSctH05k2iblGBdDcQpA== Date: Mon, 1 Mar 2021 13:04:55 +0000 Message-ID: References: <1614502908.6594.6.camel@trentalancia.com> <443d92dd844e329bcd40a1e59b7cc3784ed3db94.camel@HansenPartnership.com> <1614582394.13266.11.camel@trentalancia.com> <1614598394.4338.18.camel@trentalancia.com> <1614602388.6918.8.camel@trentalancia.com> <1614603429.6918.18.camel@trentalancia.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: trentalancia.com; dkim=none (message not signed) header.d=none;trentalancia.com; dmarc=none action=none header.from=wdc.com; x-originating-ip: [2400:2411:43c0:6000:347a:bb00:3286:307b] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 6c6f097d-bb17-4d2d-ef96-08d8dcb29c50 x-ms-traffictypediagnostic: BL0PR04MB6482: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:6430; 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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: 6c6f097d-bb17-4d2d-ef96-08d8dcb29c50 X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Mar 2021 13:04:55.7256 (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: WLrl8gRmK6hi6KuacD+FwH0RdhV4njwsPBzZGRH0Ih8u+fqQY46v0X5zMzyegHrD+18Ll7H7xVhoPkWPOP0JYA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR04MB6482 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 2021/03/01 21:57, Guido Trentalancia wrote:=0A= > On Mon, 01/03/2021 at 12.51 +0000, Damien Le Moal wrote:=0A= >> On 2021/03/01 21:39, Guido Trentalancia wrote:=0A= >>> If the system is shut down before the sync or drive unmounting and=0A= >>> the=0A= >>> write cache is enabled, there might be the loss of data in the=0A= >>> cache,=0A= >>> but this is because of the way the drive is designed.=0A= >>=0A= >> That drive is not usable. Even the best journaling file system would=0A= >> get corrupted.=0A= > =0A= > It is usable and an ext3 filesystem has not been causing any problem=0A= > for over a year now.=0A= =0A= Yes, I believe that: your patch disables the write cache ! So no synchroniz= e=0A= cache command, no caching, no data loss. All good.=0A= =0A= > =0A= >>> I believe the kernel should support the drive as it is - plug and=0A= >>> play=0A= >>> - without requiring cumbersome configurations.=0A= >>=0A= >> No. That would be lying to the user. The user expect things to work.=0A= >> Not data=0A= >> corruptions.=0A= > =0A= > Data corruption is what occurs with the current kernel when one of such= =0A= > drives is mounted.=0A= =0A= Because the drive does not have synchronize cache while caching data, which= is=0A= crazy.=0A= =0A= > With the patch the drive can be used normally and no data corruption=0A= > occurs with the drive that I have tested.=0A= =0A= Sure, because you end up with WCE=3D0. All good.=0A= =0A= > This is a proposed patch and nobody is lying, I can report the specific= =0A= > drive model that I have tested and the tests can be easily replicated=0A= > to confirm my findings.=0A= =0A= I understand the situation perfectly. I am not doubting your result. I look= ed at=0A= your patch and understand it. It is sensible, but does not plug all the pos= sible=0A= holes with such weird drive. So that is not a good solution to me.=0A= =0A= The alternative, safe this one, is a udev rule disabling your drive write c= ache=0A= or you setting the permanent drive config with WCE=3D0. That will have *exa= ctly*=0A= the same effect as your patch: things will work just fine. Try that solutio= n=0A= please. No need for a kernel patch.=0A= =0A= > =0A= > Guido=0A= > =0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=