Re: [nfsv4] RFC 7530: Available attributes for READDIR and Absent File Systems

> Do I miss something or RFC 7530 and RFC 5661 don’t have full set of
available attributes
> for an absent filesystem that can be got in READDIR operation?

These documents do not specify a full list of available attributes for
absent file systems.  The idea is that what attributes might or might not
be available is up to the server-side file system code. The general
expectation is that very little will be available.

In the case in which you are doing a READDIR within the absent file system,
 no attributes can be provided, since the operation is to be failed with
NFS4ERR_MOVED.

The other relevant case for READDIR is one in which the operation is being
done in a directory within a present file system and some of objects within
the directory are the roots of absent file systems.  Given that context,
the document could have been clearer if it had mentioned fsid and
mounted_on_filled which need to be provided  (it is a SHOULD) for GETATTR.
At the time RFC7530 was done we could have made these "SHOULD"s as they are
for GETATTR but we didn't do that since this is not a very important case
and the client has the option to follow up with GETATTR.

As it is, the server MAY return these attributes.  If one is doing a
server-side implementation, it is best to to provide them since they need
to be available for GETATTR.  On the other hand, if one is doing a
client-side implementation, you can't assume they will be present and need
to be prepared to follow up with an OTW GETATTR (which has to specify
fs_locations to prevent it from being rejected).

On May 20, 2017 3:58 PM, "Vitaliy Gusev" <gusev.vitaliy@gmail.com> wrote:

> Hi!
>
> During improving NFS v4 illumos server for READDIR operation I got question
> about availability of attributes for READDIR in case of an absent
> filesystem.
>
> RFC 7530 Section 8.3.2 “READDIR and Absent File Systems*”* says only
> about:
>
>    - fs_locations
>    -
>
>    rdattr_error
>
>
> and doesn’t specify other available attributes.
>
> Section 8.3.1 specifies attributes for an absent filesystem but only for
> GETATTR operation:
>
>    -
>
>    fs_locations
>
>    - fsid
>    -
>
>    mounted_on_fileid
>
>
>
> Do I miss something or RFC 7530 and RFC 5661 don’t have full set of
> available attributes
> for an absent filesystem that can be got in READDIR operation?
>
> ———
> Thanks,
> Vitaliy Gusev
>
>
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