Re: New copyfile system call - discuss before LSF?

From: Myklebust, Trond
Date: Thu Feb 21 2013 - 08:52:01 EST

On Thu, 2013-02-21 at 12:37 +0100, 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.

sendfile64() pretty much already has the right arguments for a
"copyfile", however it would be nice to add a 'flags' parameter: the
NFSv4.2 version would use that to specify whether or not to copy file

> 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.
> 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 :) ?

I'm planning on soon dusting off the NFS prototype that NetApp wrote 3
years ago and converting at least the client implementation into
something that can go upstream. We do also have a server prototype for
Linux, but the copy offload between 2 different servers is a hack and
would need significant work.

Trond Myklebust
Linux NFS client maintainer

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