[nfsv4] proposed change for RFC 8881 bis

[Jeff Layton <[e-mail]>]

I've been working on a draft implementation of directory delegations for
the Linux client and server. RFC 8881 says in section 18.39.3:

"The server may refuse to grant the delegation. In that case, the server
will return NFS4ERR_DIRDELEG_UNAVAIL."

...and later:

"If the server does not wish to honor the "want" or is not able to do
so, it returns the error NFS4ERR_DIRDELEG_UNAVAIL."

This behavior is straightforward to implement, but it seems sub-optimal
to have the server return a hard error in these situations, since it
will cause compound processing to abort. Acquiring a delegation is an
optimization, and failure to get one ought not be fatal.

Could we change it so that in either situation, we can have the server
optionally return NFS4_OK + GDD4_UNAVAIL instead of
NFS4ERR_DIRDELEG_UNAVAIL? That would allow later compound operations to
proceed, and would be less expensive than having to redrive a whole RPC.

Thoughts?

I'm happy to draft up a proposed change if someone can point me in the
right direction.

Thanks,
-- 
Jeff Layton <[e-mail]>