linux-kernel - Re: New copyfile system call

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Date:	Thu, 21 Feb 2013 13:51:53 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Ric Wheeler <rwheeler@...hat.com>
CC:	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Chris L. Mason" <clmason@...ionio.com>,
	Christoph Hellwig <hch@...radead.org>,
	Alexander Viro <aviro@...hat.com>,
	"Martin K. Petersen" <mkp@....net>, Hannes Reinecke <hare@...e.de>
Subject: Re: New copyfile system call - discuss before LSF?

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
metadata.

> 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

NetApp
Trond.Myklebust@...app.com
www.netapp.com
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