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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: PH0PR04MB7416.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: f5f3f2af-e100-48eb-e8dc-08da3a413a5b X-MS-Exchange-CrossTenant-originalarrivaltime: 20 May 2022 09:15:05.2265 (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: DLwgx1Q+Dnwk3RsZDZxwA+SULokeFGc6+o8MCY3eY0pEYNPCBkiTMnoRUDGzCTcrYhhe8ZvQzaB8TzXx4yqZzgiYdgwwBz2ri4HAZbwk1R8= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR04MB6668 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/05/2022 11:07, Pankaj Raghav wrote:=0A= > On 5/19/22 09:57, Johannes Thumshirn wrote:=0A= >>> Unfortunately it is not possible to just move the WP in zoned devices.= =0A= >>> The only alternative that I could use is to do write zeroes which are= =0A= >>> natively supported by some devices such as ZNS. It would be nice to kno= w=0A= >>> if someone had a better solution to this instead of doing write zeroes= =0A= >>> in zoned devices.=0A= >>>=0A= >>=0A= >> I have another question. In case we need to pad the sb zone with a write= =0A= >> zeros and have a power fail between the write-zeros and the regular =0A= >> super-block write, what happens? I know this padding is only done for th= e=0A= >> backup super blocks, never the less it can happen and it can happen when= =0A= >> the primary super block is also corrupted.=0A= >>=0A= >> AFAIU we're then trying to reach out for a backup super block, look at t= he=0A= >> write pointer and it only contains zeros but no super block, as only the= =0A= >> write-zeros has reached the device and not the super block write.=0A= >>=0A= >> How is this situation handled?=0A= >>=0A= > That is a very good point. I did think about this situation while adding= =0A= > padding to the mirror superblock with write zeroes. If the drive is=0A= > **less than 4TB** and with the **primary superblock corrupted**, then it= =0A= > will be an issue with the situation you have described for npo2 drives.= =0A= > That situation is not handled here. Ofc this is not an issue when we=0A= > have the second mirror at 4TB for bigger drives. Do you have some ideas= =0A= > in mind for this failure mode?=0A= =0A= The only idea I have for this is creating a bounce buffer, write the paddin= g=0A= and the super-block into the buffer and then submit it. But that's too ugly= =0A= to live.=0A= =0A= And it would involve changing non-zoned super-block writing code, which I t= hink=0A= is way to risky.=0A=