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

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Message-ID: <CAJfpegtdiQzP7t5hc_OaHjSGTrjdZLfKi6fiKqBQ_+AP2Y0-oQ@mail.gmail.com>
Date:	Sat, 28 Sep 2013 07:49:46 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Zach Brown <zab@...hat.com>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	Ric Wheeler <rwheeler@...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>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Bryan Schumaker <bjschuma@...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 Fri, Sep 27, 2013 at 10:50 PM, Zach Brown <zab@...hat.com> wrote:
>> Also, I don't get the first option above at all.  The argument is that
>> it's safer to have more copies?  How much safety does another copy on
>> the same disk really give you?  Do systems that do dedup provide
>> interfaces to turn it off per-file?

I don't see the safety argument very compelling either.  There are
real semantic differences, however: ENOSPC on a write to a
(apparentlíy) already allocated block.  That could be a bit
unexpected.  Do we need a fallocate extension to deal with shared
blocks?

Thanks,
Miklos
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