Re: New copyfile system call - discuss before LSF?

Hannes Reinecke
2013-02-21T13:37:35Z

On 02/21/2013 12:37 PM, Ric Wheeler wrote:
>
> We have debated the need to have a system call to allow for
> offloading copy operations, for example to an NFS server (part to
> the new NFS 4.2 specification), SCSI target device (two different
> SCSI commands do this), local file systems (reflink, etc) and I
> suspect many other possible parts of the stack could implement this.
>
> The earliest discussion of such a system call I saw happened back in
> 2001, I know we had another more recent flurry (2-3 years back?) as
> well that got tangled up and died away.
>
Yeah, I remember. I talked to Mkp about it, who (as usual :-) had a
patchset stashed away for this.
Or a preliminary attempt, anyway.
However, this was waiting for the DISCARD merging patches to go in,
which in turn were waiting for the WRITE SAME patches IIRC.

Or something.

Martin?

> Given the new popularity of this in storage devices and the use case
> for virt guests, any chance to get a proposal floated this year that
> might be able to land upstream in our life times :) ?
>
Oh, most definitely.
Now that I finally have an array capable of doing ROD token copy
we should be reevaluating things.

I see to have the sg_xcopy program updated to do ROD copy, then we
will have some real-world data.

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
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