Re: [nfsv4] xattr model in draft-naik-nfsv4-xattrs-01?

[Casey Bodley <[e-mail]>]

On Sat, Oct 4, 2014 at 4:34 PM, Manoj Naik <[e-mail]> wrote:
> Christoph Hellwig <[e-mail]> wrote on 10/04/2014 09:17:50 AM:
>> On the GETXATTR side you conflate the LISTXATTR operation with GETXATTR,
>> as well as adding a new bulk get one that isn't present in any OS API
>> I know.  Both the argument and return structures are basically entirely
>> different for the different cases.
>
> Agree that GETXATTR includes what is traditionally provided by listxattr()
> call. The idea was to limit the number of new operations provided to two -
> GETXATTR and SETXATTR. But if there is consensus, we don't have an issue
> with adding a LISTXATTR instead.
>
> I think the ability to get/set all xattrs of a given file
> (getallxattrs/setallxattrs?) is useful, especially for backup/restore
> programs. Granted that there isn't an OS API that exposes this, but perhaps
> there should be one? I know some backup utilities that work directly with a
> filesystem API to do this. Especially over NFS, I believe a single RPC that
> accomplishes this may be desirable. I know somebody on the list or at the
> IETF meeting asked for this specifically too.

The Windows system calls and kernel interfaces operate on linked lists
of extended attributes. You can see their interfaces in the msdn
documentation for ZwQueryEaFile/ZwSetEaFile and
IRP_MJ_QUERY_EA/IRP_MJ_SET_EA.