Re: [RFC] extending splice for copy offloading

From: Miklos Szeredi
Date: Mon Sep 30 2013 - 11:46:46 EST

On Mon, Sep 30, 2013 at 4:41 PM, Ric Wheeler <rwheeler@xxxxxxxxxx> wrote:
> The way the array based offload (and some software side reflink works) is
> not a byte by byte copy. We cannot assume that a valid count can be returned
> or that such a count would be an indication of a sequential segment of good
> data. The whole thing would normally have to be reissued.
> To make that a true assumption, you would have to mandate that in each of
> the specifications (and sw targets)...

You're missing my point.

- user issues SIZE_MAX splice request
- fs issues *64M* (or whatever) request to offload
- when that completes *fully* then we return 64M to userspace
- if it completes partially, then we return an error to userspace

Again, wouldn't that work?

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