[PATCH v20 02/12] Add infrastructure for copy offload in block and request layer.

[Christoph Hellwig]

On Wed, Jun 26, 2024 at 06:18:18AM +0900, Damien Le Moal wrote:
> 
> DM can deal with "abnormal" BIOs on its own. There is code for that.
> See is_abnormal_io() and __process_abnormal_io(). Sure, that will need more code
> compared to a bio sector+size based simple split, but I do not think it is a big
> deal given the potential benefits of the offloading.

It's not just dm.  You also need it in the partition remapping code
(mandatory), md (nice to have), etc.

And then we have the whole mess of what is in the payload for the I/O
stack vs what is in the payload for the on the wire protocol, which
will have different formatting and potentially also different sizes.