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Re: [nfsv4] Server-side copy question

"J. Bruce Fields" <bfields@fieldses.org> Tue, 24 October 2017 18:38 UTC

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Date: Tue, 24 Oct 2017 14:38:03 -0400
From: "J. Bruce Fields" <bfields@fieldses.org>
To: Olga Kornievskaia <aglo@citi.umich.edu>
Cc: David Noveck <davenoveck@gmail.com>, "nfsv4@ietf.org" <nfsv4@ietf.org>
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Subject: Re: [nfsv4] Server-side copy question
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I said:
> >>I guess I'd be in favor of using the NFS_OK branch of CB_OFFLOAD
> >> whenever a nonzero number of bytes is copied.

On Tue, Oct 24, 2017 at 11:52:17AM -0400, Olga Kornievskaia wrote:
> On Tue, Oct 24, 2017 at 7:43 AM, David Noveck <davenoveck@gmail.com> wrote:
> >
> > That's likely to create an interoperability problem, since there are
> > almost certainly clients who assume that when there is no error, all
> > requested bytes have been copied.
> 
> I don't think it's true that clients would assume this. I think the
> client can only assume server copied as many bytes as it was specified
> in the CB_OFFLOAD bytes_copied regardless of how many bytes the client
> had asked for. At least that's how I read the spec.

Agreed.  CB_OFFLOAD has a wr_count field in the NFS_OK branch, what else
could it possibly be for?  And there's ample precedent (e.g. in READ and
WRITE) for succesful IO operations returning a count value that's
possibly less than what's requested.

--b.

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