On 1/30/2025 6:23 PM, Christoph Hellwig wrote: >> Difference is that FS does not have to attach any PI for offload. >> >> Offload is about the Host doing as little as possible, and the closest >> we get there is by setting PRACT bit. > But that doesn't actually work. The file system needs to be able > to verify the checksum for failing over to other mirrors, repair, > etc. Right. That sounds like reusing the existing code on detecting checksum-specific failure. So maybe that can be handled iff this gets any far. > Also if you trust the device to get things right you do not > need to use PI at all - SSDs or hard drives that support PI generally > use PI internally anyway, and PRACT just means you treat a format > with PI like one without. In other words - no need for an offload > here, you might as well just trust the device if you're not doing > end to end protection. Agree that device maybe implementing internal E2E, but that's not a contract to be honored. Host can't trust until device says it explicitly. Since Btrfs already has 'nodatasum' mount option, I assume there are deployments that prefer to optimize for checksum. I thought Btrfs will be more comfortable to give up (its own checksum tree) and exercise this more often if it certainly knows that device is also capable.
