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Date:   Sun, 21 Feb 2021 04:19:21 +0900
From:   Keith Busch <kbusch@kernel.org>
To:     David Laight <David.Laight@aculab.com>
Cc:     'SelvaKumar S' <selvakuma.s1@samsung.com>,
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Subject: Re: [RFC PATCH v5 0/4] add simple copy support
Message-ID: <20210220191921.GA7968@redsun51.ssa.fujisawa.hgst.com>
References: <CGME20210219124555epcas5p1334e7c4d64ada5dc4a2ca0feb48c1d44@epcas5p1.samsung.com>
 <20210219124517.79359-1-selvakuma.s1@samsung.com>
 <146c47907c2446d4a896830de400dd81@AcuMS.aculab.com>
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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.