[LSF/MM/BPF TOPIC] File system checksum offload

[Kanchan Joshi]

On 2/3/2025 1:46 PM, Qu Wenruo wrote:
>> ell for the WAF part, it'll save us 32 Bytes per FS sector (typically
>> 4k) in the btrfs case, that's ~0.8% of the space.
> 
> You forgot the csum tree COW part.
> 
> Updating csum tree is pretty COW heavy and that's going to cause quite 
> some wearing.
> 
> Thus although I do not think the RFC patch makes much sense compared to 
> just existing NODATASUM mount option, I'm interesting in the hardware 
> csum handling.

But, patches do exactly that i.e., hardware cusm support. And posted 
numbers [*] are also when hardware is checksumming the data blocks.

NODATASUM forgoes the data cums at Btrfs level, but its scope of 
control/influence ends there, as it knows nothing about what happens 
underneath.
Proposed option (DATASUM_OFFLOAD) ensures that the [only] hardware 
checksums the data blocks.

[*] 
https://lore.kernel.org/linux-block/20250129140207.22718-1-joshi.k@samsung.com/