NFSv4.1 Server Implementation

Server support for minorversion 1 can be controlled using the
/proc/fs/nfsd/versions control file.  The string output returned
by reading this file will contain either "+4.1" or "-4.1"
correspondingly.

Currently, server support for minorversion 1 is disabled by default.
It can be enabled at run time by writing the string "+4.1" to
the /proc/fs/nfsd/versions control file.  Note that to write this
control file, the nfsd service must be taken down.  Use your user-mode
nfs-utils to set this up; see rpc.nfsd(8)

The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based
on the latest NFSv4.1 Internet Draft:
http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-29

From the many new features in NFSv4.1 the current implementation
focuses on the mandatory-to-implement NFSv4.1 Sessions, providing
"exactly once" semantics and better control and throttling of the
resources allocated for each client.

Other NFSv4.1 features, Parallel NFS operations in particular,
are still under development out of tree.
See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design
for more information.

The table below, taken from the NFSv4.1 document, lists
the operations that are mandatory to implement (REQ), optional
(OPT), and NFSv4.0 operations that are required not to implement (MNI)
in minor version 1.  The first column indicates the operations that
are not supported yet by the linux server implementation.

The OPTIONAL features identified and their abbreviations are as follows:
	pNFS	Parallel NFS
	FDELG	File Delegations
	DDELG	Directory Delegations

The following abbreviations indicate the linux server implementation status.
	I	Implemented NFSv4.1 operations.
	NS	Not Supported.
	NS*	unimplemented optional feature.
	P	pNFS features implemented out of tree.
	PNS	pNFS features that are not supported yet (out of tree).

Operations

   +----------------------+------------+--------------+----------------+
   | Operation            | REQ, REC,  | Feature      | Definition     |
   |                      | OPT, or    | (REQ, REC,   |                |
   |                      | MNI        | or OPT)      |                |
   +----------------------+------------+--------------+----------------+
   | ACCESS               | REQ        |              | Section 18.1   |
NS | BACKCHANNEL_CTL      | REQ        |              | Section 18.33  |
NS | BIND_CONN_TO_SESSION | REQ        |              | Section 18.34  |
   | CLOSE                | REQ        |              | Section 18.2   |
   | COMMIT               | REQ        |              | Section 18.3   |
   | CREATE               | REQ        |              | Section 18.4   |
I  | CREATE_SESSION       | REQ        |              | Section 18.36  |
NS*| DELEGPURGE           | OPT        | FDELG (REQ)  | Section 18.5   |
   | DELEGRETURN          | OPT        | FDELG,       | Section 18.6   |
   |                      |            | DDELG, pNFS  |                |
   |                      |            | (REQ)        |                |
NS | DESTROY_CLIENTID     | REQ        |              | Section 18.50  |
I  | DESTROY_SESSION      | REQ        |              | Section 18.37  |
I  | EXCHANGE_ID          | REQ        |              | Section 18.35  |
NS | FREE_STATEID         | REQ        |              | Section 18.38  |
   | GETATTR              | REQ        |              | Section 18.7   |
P  | GETDEVICEINFO        | OPT        | pNFS (REQ)   | Section 18.40  |
P  | GETDEVICELIST        | OPT        | pNFS (OPT)   | Section 18.41  |
   | GETFH                | REQ        |              | Section 18.8   |
NS*| GET_DIR_DELEGATION   | OPT        | DDELG (REQ)  | Section 18.39  |
P  | LAYOUTCOMMIT         | OPT        | pNFS (REQ)   | Section 18.42  |
P  | LAYOUTGET            | OPT        | pNFS (REQ)   | Section 18.43  |
P  | LAYOUTRETURN         | OPT        | pNFS (REQ)   | Section 18.44  |
   | LINK                 | OPT        |              | Section 18.9   |
   | LOCK                 | REQ        |              | Section 18.10  |
   | LOCKT                | REQ        |              | Section 18.11  |
   | LOCKU                | REQ        |              | Section 18.12  |
   | LOOKUP               | REQ        |              | Section 18.13  |
   | LOOKUPP              | REQ        |              | Section 18.14  |
   | NVERIFY              | REQ        |              | Section 18.15  |
   | OPEN                 | REQ        |              | Section 18.16  |
NS*| OPENATTR             | OPT        |              | Section 18.17  |
   | OPEN_CONFIRM         | MNI        |              | N/A            |
   | OPEN_DOWNGRADE       | REQ        |              | Section 18.18  |
   | PUTFH                | REQ        |              | Section 18.19  |
   | PUTPUBFH             | REQ        |              | Section 18.20  |
   | PUTROOTFH            | REQ        |              | Section 18.21  |
   | READ                 | REQ        |              | Section 18.22  |
   | READDIR              | REQ        |              | Section 18.23  |
   | READLINK             | OPT        |              | Section 18.24  |
NS | RECLAIM_COMPLETE     | REQ        |              | Section 18.51  |
   | RELEASE_LOCKOWNER    | MNI        |              | N/A            |
   | REMOVE               | REQ        |              | Section 18.25  |
   | RENAME               | REQ        |              | Section 18.26  |
   | RENEW                | MNI        |              | N/A            |
   | RESTOREFH            | REQ        |              | Section 18.27  |
   | SAVEFH               | REQ        |              | Section 18.28  |
   | SECINFO              | REQ        |              | Section 18.29  |
NS | SECINFO_NO_NAME      | REC        | pNFS files   | Section 18.45, |
   |                      |            | layout (REQ) | Section 13.12  |
I  | SEQUENCE             | REQ        |              | Section 18.46  |
   | SETATTR              | REQ        |              | Section 18.30  |
   | SETCLIENTID          | MNI        |              | N/A            |
   | SETCLIENTID_CONFIRM  | MNI        |              | N/A            |
NS | SET_SSV              | REQ        |              | Section 18.47  |
NS | TEST_STATEID         | REQ        |              | Section 18.48  |
   | VERIFY               | REQ        |              | Section 18.31  |
NS*| WANT_DELEGATION      | OPT        | FDELG (OPT)  | Section 18.49  |
   | WRITE                | REQ        |              | Section 18.32  |

Callback Operations

   +-------------------------+-----------+-------------+---------------+
   | Operation               | REQ, REC, | Feature     | Definition    |
   |                         | OPT, or   | (REQ, REC,  |               |
   |                         | MNI       | or OPT)     |               |
   +-------------------------+-----------+-------------+---------------+
   | CB_GETATTR              | OPT       | FDELG (REQ) | Section 20.1  |
P  | CB_LAYOUTRECALL         | OPT       | pNFS (REQ)  | Section 20.3  |
NS*| CB_NOTIFY               | OPT       | DDELG (REQ) | Section 20.4  |
P  | CB_NOTIFY_DEVICEID      | OPT       | pNFS (OPT)  | Section 20.12 |
NS*| CB_NOTIFY_LOCK          | OPT       |             | Section 20.11 |
NS*| CB_PUSH_DELEG           | OPT       | FDELG (OPT) | Section 20.5  |
   | CB_RECALL               | OPT       | FDELG,      | Section 20.2  |
   |                         |           | DDELG, pNFS |               |
   |                         |           | (REQ)       |               |
NS*| CB_RECALL_ANY           | OPT       | FDELG,      | Section 20.6  |
   |                         |           | DDELG, pNFS |               |
   |                         |           | (REQ)       |               |
NS | CB_RECALL_SLOT          | REQ       |             | Section 20.8  |
NS*| CB_RECALLABLE_OBJ_AVAIL | OPT       | DDELG, pNFS | Section 20.7  |
   |                         |           | (REQ)       |               |
I  | CB_SEQUENCE             | OPT       | FDELG,      | Section 20.9  |
   |                         |           | DDELG, pNFS |               |
   |                         |           | (REQ)       |               |
NS*| CB_WANTS_CANCELLED      | OPT       | FDELG,      | Section 20.10 |
   |                         |           | DDELG, pNFS |               |
   |                         |           | (REQ)       |               |
   +-------------------------+-----------+-------------+---------------+

Implementation notes:

EXCHANGE_ID:
* only SP4_NONE state protection supported
* implementation ids are ignored

CREATE_SESSION:
* backchannel attributes are ignored
* backchannel security parameters are ignored

SEQUENCE:
* no support for dynamic slot table renegotiation (optional)

nfsv4.1 COMPOUND rules:
The following cases aren't supported yet:
* Enforcing of NFS4ERR_NOT_ONLY_OP for: BIND_CONN_TO_SESSION, CREATE_SESSION,
  DESTROY_CLIENTID, DESTROY_SESSION, EXCHANGE_ID.
* DESTROY_SESSION MUST be the final operation in the COMPOUND request.

