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Subject: Re: copy offload support and absent file system
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <CAN-5tyEn+mM8ucuPXawN9L57XyGHUQHNL6Ddic5TFdXYTY2bSg@mail.gmail.com>
Date:   Fri, 26 Oct 2018 11:04:17 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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To:     Olga Kornievskaia <aglo@umich.edu>
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> On Oct 26, 2018, at 8:54 AM, Olga Kornievskaia <aglo@umich.edu> wrote:
> 
> Hi Chuck,
> 
> In the context of doing a copy between different "types" of
> filesystems, it was pointed out to me that NFS has many types:
> nfs4_fs_type, nfs4_remote_fs_type, nfs4_remote_referral_fs_type,
> nfs4_referral_fs_type. So doing a simple check that fs type of "in"
> and "out" might not be sufficient. Do you see any issues allowing a
> copy offload between different types? Basically checking that "in" and
> "out" descriptions come from any of the these types?

I'm no expert... so what follows is an uninformed opinion.

All of these are NFSv4 file systems. But I don't think that's an
adequate check (it's necessary, but not sufficient).

The minor version of the mount point has to be 2 or higher, and
the client must confirm that the mounted server supports copy
offload (because all NFSv4.2 features are OPTIONAL).


--
Chuck Lever