[PATCH 1/5] block: new sector copy api

[Christoph Hellwig]

On Wed, May 21, 2025 at 03:31:03PM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch at kernel.org>
> 
> Provide a basic block level api to copy a range of a block device's
> sectors to a new destination on the same device. This just reads the
> source data into host memory, then writes it back out to the device at
> the requested destination.

As someone who recently spent a lot of time on optimizing such loops:
having a general API that allocates a buffer for each copy is a bad
idea.  You'll want some kind of caller provided longer living allocation
if you do regularly do such copies.

Maybe having common code is good to avoid copies, but I suspect most
real users would want their own.