Messages in this thread | | | Date | Mon, 30 Sep 2013 09:49:12 -0500 | From | Ric Wheeler <> | Subject | Re: [RFC] extending splice for copy offloading |
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On 09/30/2013 10:46 AM, Miklos Szeredi wrote: > On Mon, Sep 30, 2013 at 4:41 PM, Ric Wheeler <rwheeler@redhat.com> wrote: >> The way the array based offload (and some software side reflink works) is >> not a byte by byte copy. We cannot assume that a valid count can be returned >> or that such a count would be an indication of a sequential segment of good >> data. The whole thing would normally have to be reissued. >> >> To make that a true assumption, you would have to mandate that in each of >> the specifications (and sw targets)... > You're missing my point. > > - user issues SIZE_MAX splice request > - fs issues *64M* (or whatever) request to offload > - when that completes *fully* then we return 64M to userspace > - if it completes partially, then we return an error to userspace > > Again, wouldn't that work? > > Thanks, > Miklos
Yes, if you send a copy offload command and it works, you can assume that it worked fully. It would be pretty interesting if that were not true :)
If it fails, we cannot assume anything about partial completion.
Ric
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