Re: [PATCH v13 1/9] block: Introduce queue limits for copy-offload support

Christoph Hellwig
2023-07-20T07:06:41Z

Just a little heads up: I think we need to properly solve the
hw vs user limit as the various ad-hoc mechanisms tend to be
broken and don't scale. I plan to start looking into that the
next days.

On Wed, Jun 28, 2023 at 12:06:15AM +0530, Nitesh Shetty wrote:
> Add device limits as sysfs entries,
> - copy_offload (RW)
> - copy_max_bytes (RW)
> - copy_max_bytes_hw (RO)
>
> Above limits help to split the copy payload in block layer.
> copy_offload: used for setting copy offload(1) or emulation(0).
> copy_max_bytes: maximum total length of copy in single payload.
> copy_max_bytes_hw: Reflects the device supported maximum limit.

Why do we need the separate copy_offload boolean vs just looking
at the max_bytes value?