Re: [RFC PATCH v5 0/4] add simple copy support

[Keith Busch]

On Sat, Feb 20, 2021 at 06:01:56PM +0000, David Laight wrote:
> From: SelvaKumar S
> > Sent: 19 February 2021 12:45
> > 
> > This patchset tries to add support for TP4065a ("Simple Copy Command"),
> > v2020.05.04 ("Ratified")
> > 
> > The Specification can be found in following link.
> > https://nvmexpress.org/wp-content/uploads/NVM-Express-1.4-Ratified-TPs-1.zip
> > 
> > Simple copy command is a copy offloading operation and is  used to copy
> > multiple contiguous ranges (source_ranges) of LBA's to a single destination
> > LBA within the device reducing traffic between host and device.
> 
> Sounds to me like the real reason is that the copy just ends up changing
> some indirect block pointers rather than having to actually copy the data.

I guess an implementation could do that, but I think that's missing the
point of the command. The intention is to copy the data to a new
location on the media for host managed garbage collection.