# Re: \[PATCH 3/7\] block: copy offload support infrastructure

- From: Bart Van Assche \<bvanassche@acm.org\>
- Date: 2021-08-17 17:14:33 
- List: linux-block
- Page: https://ratatoskr.run/linux-block/2021/08/212604
- Thread: https://ratatoskr.run/linux-nvme/2021/08/212564/t.md

```text
On 8/17/21 3:14 AM, SelvaKumar S wrote:
> Introduce REQ_OP_COPY, a no-merge copy offload operation. Create
> bio with control information as payload and submit to the device.
> Larger copy operation may be divided if necessary by looking at device
> limits. REQ_OP_COPY(19) is a write op and takes zone_write_lock when
> submitted to zoned device.
> Native copy offload is not supported for stacked devices.

Using a single operation for copy-offloading instead of separate operations for reading and writing is fundamentally incompatible with the device mapper. I think we need a copy-offloading implementation that is compatible with the device mapper.

Storing the parameters of the copy operation in the bio payload is incompatible with the current implementation of bio_split().

In other words, I think there are fundamental problems with this patch series.

Bart.
```