Re: New copyfile system call - discuss before LSF?

From: Hannes Reinecke
Date: Thu Feb 21 2013 - 08:37:40 EST

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.


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.


Dr. Hannes Reinecke zSeries & Storage
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SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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