[PATCH v15 09/12] dm: Add support for copy offload

[Nitesh Shetty]

On Fri, Sep 08, 2023 at 08:13:37AM +0200, Hannes Reinecke wrote:
> On 9/6/23 18:38, Nitesh Shetty wrote:
> > Before enabling copy for dm target, check if underlying devices and
> > dm target support copy. Avoid split happening inside dm target.
> > Fail early if the request needs split, currently splitting copy
> > request is not supported.
> > 
> And here is where I would have expected the emulation to take place;
> didn't you have it in one of the earlier iterations?

No, but it was the other way round.
In dm-kcopyd we used device offload, if that was possible, before using default
dm-mapper copy. It was dropped in the current series,
to streamline the patches and make the series easier to review.

> After all, device-mapper already has the infrastructure for copying
> data between devices, so adding a copy-offload emulation for device-mapper
> should be trivial.
I did not understand this, can you please elaborate ?

Thank you,
Nitesh Shetty