On 20/05/2022 11:07, Pankaj Raghav wrote: > On 5/19/22 09:57, Johannes Thumshirn wrote: >>> Unfortunately it is not possible to just move the WP in zoned devices. >>> The only alternative that I could use is to do write zeroes which are >>> natively supported by some devices such as ZNS. It would be nice to know >>> if someone had a better solution to this instead of doing write zeroes >>> in zoned devices. >>> >> >> I have another question. In case we need to pad the sb zone with a write >> zeros and have a power fail between the write-zeros and the regular >> super-block write, what happens? I know this padding is only done for the >> backup super blocks, never the less it can happen and it can happen when >> the primary super block is also corrupted. >> >> AFAIU we're then trying to reach out for a backup super block, look at the >> write pointer and it only contains zeros but no super block, as only the >> write-zeros has reached the device and not the super block write. >> >> How is this situation handled? >> > That is a very good point. I did think about this situation while adding > padding to the mirror superblock with write zeroes. If the drive is > **less than 4TB** and with the **primary superblock corrupted**, then it > will be an issue with the situation you have described for npo2 drives. > That situation is not handled here. Ofc this is not an issue when we > have the second mirror at 4TB for bigger drives. Do you have some ideas > in mind for this failure mode? The only idea I have for this is creating a bounce buffer, write the padding and the super-block into the buffer and then submit it. But that's too ugly to live. And it would involve changing non-zoned super-block writing code, which I think is way to risky.
