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Date: Sat, 28 Sep 2013 07:49:46 +0200
Message-ID: <CAJfpegtdiQzP7t5hc_OaHjSGTrjdZLfKi6fiKqBQ_+AP2Y0-oQ@mail.gmail.com>
Subject: Re: [RFC] extending splice for copy offloading
From: Miklos Szeredi <miklos@szeredi.hu>
To: Zach Brown <zab@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
        Ric Wheeler <rwheeler@redhat.com>,
        Anna Schumaker <schumaker.anna@gmail.com>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        Trond Myklebust <Trond.Myklebust@netapp.com>,
        Bryan Schumaker <bjschuma@netapp.com>,
        "Martin K. Petersen" <mkp@mkp.net>, Jens Axboe <axboe@kernel.dk>,
        Mark Fasheh <mfasheh@suse.com>, Joel Becker <jlbec@evilplan.org>,
        Eric Wong <normalperson@yhbt.net>
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On Fri, Sep 27, 2013 at 10:50 PM, Zach Brown <zab@redhat.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