linux-kernel - Re: [RFC] extending splice for copy offloading

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Date:	Mon, 30 Sep 2013 18:02:08 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>
CC:	Miklos Szeredi <miklos@...redi.hu>,
	Ric Wheeler <rwheeler@...hat.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Zach Brown <zab@...hat.com>,
	"Anna Schumaker" <schumaker.anna@...il.com>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"Schumaker, Bryan" <Bryan.Schumaker@...app.com>,
	"Martin K. Petersen" <mkp@....net>, Jens Axboe <axboe@...nel.dk>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>,
	Eric Wong <normalperson@...t.net>
Subject: Re: [RFC] extending splice for copy offloading

On Mon, 2013-09-30 at 19:48 +0200, Bernd Schubert wrote:
> On 09/30/2013 07:44 PM, Myklebust, Trond wrote:
> > On Mon, 2013-09-30 at 19:17 +0200, Bernd Schubert wrote:
> >> It would be nice if there would be way if the file system would get a
> >> hint that the target file is supposed to be copy of another file. That
> >> way distributed file systems could also create the target-file with the
> >> correct meta-information (same storage targets as in-file has).
> >> Well, if we cannot agree on that, file system with a custom protocol at
> >> least can detect from 0 to SSIZE_MAX and then reset metadata. I'm not
> >> sure if this would work for pNFS, though.
> >
> > splice() does not create new files. What you appear to be asking for
> > lies way outside the scope of that system call interface.
> >
> 
> Sorry I know, definitely outside the scope of splice, but in the context 
> of offloaded file copies. So the question is, what is the best way to 
> address/discuss that?

Why does it need to be addressed in the first place?

What is preventing an application from retrieving and setting this
information using standard libc functions such as fstat()+open(), and
supplemented with libattr attr_setf/getf(), and libacl acl_get_fd/set_fd
where appropriate?

-- 
Trond Myklebust
Linux NFS client maintainer

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