1NFSv4.1 Server Implementation
2
3Server support for minorversion 1 can be controlled using the
4/proc/fs/nfsd/versions control file.  The string output returned
5by reading this file will contain either "+4.1" or "-4.1"
6correspondingly.
7
8Currently, server support for minorversion 1 is enabled by default.
9It can be disabled at run time by writing the string "-4.1" to
10the /proc/fs/nfsd/versions control file.  Note that to write this
11control file, the nfsd service must be taken down.  You can use rpc.nfsd
12for this; see rpc.nfsd(8).
13
14(Warning: older servers will interpret "+4.1" and "-4.1" as "+4" and
15"-4", respectively.  Therefore, code meant to work on both new and old
16kernels must turn 4.1 on or off *before* turning support for version 4
17on or off; rpc.nfsd does this correctly.)
18
19The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based
20on RFC 5661.
21
22From the many new features in NFSv4.1 the current implementation
23focuses on the mandatory-to-implement NFSv4.1 Sessions, providing
24"exactly once" semantics and better control and throttling of the
25resources allocated for each client.
26
27The table below, taken from the NFSv4.1 document, lists
28the operations that are mandatory to implement (REQ), optional
29(OPT), and NFSv4.0 operations that are required not to implement (MNI)
30in minor version 1.  The first column indicates the operations that
31are not supported yet by the linux server implementation.
32
33The OPTIONAL features identified and their abbreviations are as follows:
34	pNFS	Parallel NFS
35	FDELG	File Delegations
36	DDELG	Directory Delegations
37
38The following abbreviations indicate the linux server implementation status.
39	I	Implemented NFSv4.1 operations.
40	NS	Not Supported.
41	NS*	Unimplemented optional feature.
42
43Operations
44
45   +----------------------+------------+--------------+----------------+
46   | Operation            | REQ, REC,  | Feature      | Definition     |
47   |                      | OPT, or    | (REQ, REC,   |                |
48   |                      | MNI        | or OPT)      |                |
49   +----------------------+------------+--------------+----------------+
50   | ACCESS               | REQ        |              | Section 18.1   |
51I  | BACKCHANNEL_CTL      | REQ        |              | Section 18.33  |
52I  | BIND_CONN_TO_SESSION | REQ        |              | Section 18.34  |
53   | CLOSE                | REQ        |              | Section 18.2   |
54   | COMMIT               | REQ        |              | Section 18.3   |
55   | CREATE               | REQ        |              | Section 18.4   |
56I  | CREATE_SESSION       | REQ        |              | Section 18.36  |
57NS*| DELEGPURGE           | OPT        | FDELG (REQ)  | Section 18.5   |
58   | DELEGRETURN          | OPT        | FDELG,       | Section 18.6   |
59   |                      |            | DDELG, pNFS  |                |
60   |                      |            | (REQ)        |                |
61I  | DESTROY_CLIENTID     | REQ        |              | Section 18.50  |
62I  | DESTROY_SESSION      | REQ        |              | Section 18.37  |
63I  | EXCHANGE_ID          | REQ        |              | Section 18.35  |
64I  | FREE_STATEID         | REQ        |              | Section 18.38  |
65   | GETATTR              | REQ        |              | Section 18.7   |
66I  | GETDEVICEINFO        | OPT        | pNFS (REQ)   | Section 18.40  |
67NS*| GETDEVICELIST        | OPT        | pNFS (OPT)   | Section 18.41  |
68   | GETFH                | REQ        |              | Section 18.8   |
69NS*| GET_DIR_DELEGATION   | OPT        | DDELG (REQ)  | Section 18.39  |
70I  | LAYOUTCOMMIT         | OPT        | pNFS (REQ)   | Section 18.42  |
71I  | LAYOUTGET            | OPT        | pNFS (REQ)   | Section 18.43  |
72I  | LAYOUTRETURN         | OPT        | pNFS (REQ)   | Section 18.44  |
73   | LINK                 | OPT        |              | Section 18.9   |
74   | LOCK                 | REQ        |              | Section 18.10  |
75   | LOCKT                | REQ        |              | Section 18.11  |
76   | LOCKU                | REQ        |              | Section 18.12  |
77   | LOOKUP               | REQ        |              | Section 18.13  |
78   | LOOKUPP              | REQ        |              | Section 18.14  |
79   | NVERIFY              | REQ        |              | Section 18.15  |
80   | OPEN                 | REQ        |              | Section 18.16  |
81NS*| OPENATTR             | OPT        |              | Section 18.17  |
82   | OPEN_CONFIRM         | MNI        |              | N/A            |
83   | OPEN_DOWNGRADE       | REQ        |              | Section 18.18  |
84   | PUTFH                | REQ        |              | Section 18.19  |
85   | PUTPUBFH             | REQ        |              | Section 18.20  |
86   | PUTROOTFH            | REQ        |              | Section 18.21  |
87   | READ                 | REQ        |              | Section 18.22  |
88   | READDIR              | REQ        |              | Section 18.23  |
89   | READLINK             | OPT        |              | Section 18.24  |
90   | RECLAIM_COMPLETE     | REQ        |              | Section 18.51  |
91   | RELEASE_LOCKOWNER    | MNI        |              | N/A            |
92   | REMOVE               | REQ        |              | Section 18.25  |
93   | RENAME               | REQ        |              | Section 18.26  |
94   | RENEW                | MNI        |              | N/A            |
95   | RESTOREFH            | REQ        |              | Section 18.27  |
96   | SAVEFH               | REQ        |              | Section 18.28  |
97   | SECINFO              | REQ        |              | Section 18.29  |
98I  | SECINFO_NO_NAME      | REC        | pNFS files   | Section 18.45, |
99   |                      |            | layout (REQ) | Section 13.12  |
100I  | SEQUENCE             | REQ        |              | Section 18.46  |
101   | SETATTR              | REQ        |              | Section 18.30  |
102   | SETCLIENTID          | MNI        |              | N/A            |
103   | SETCLIENTID_CONFIRM  | MNI        |              | N/A            |
104NS | SET_SSV              | REQ        |              | Section 18.47  |
105I  | TEST_STATEID         | REQ        |              | Section 18.48  |
106   | VERIFY               | REQ        |              | Section 18.31  |
107NS*| WANT_DELEGATION      | OPT        | FDELG (OPT)  | Section 18.49  |
108   | WRITE                | REQ        |              | Section 18.32  |
109
110Callback Operations
111
112   +-------------------------+-----------+-------------+---------------+
113   | Operation               | REQ, REC, | Feature     | Definition    |
114   |                         | OPT, or   | (REQ, REC,  |               |
115   |                         | MNI       | or OPT)     |               |
116   +-------------------------+-----------+-------------+---------------+
117   | CB_GETATTR              | OPT       | FDELG (REQ) | Section 20.1  |
118I  | CB_LAYOUTRECALL         | OPT       | pNFS (REQ)  | Section 20.3  |
119NS*| CB_NOTIFY               | OPT       | DDELG (REQ) | Section 20.4  |
120NS*| CB_NOTIFY_DEVICEID      | OPT       | pNFS (OPT)  | Section 20.12 |
121NS*| CB_NOTIFY_LOCK          | OPT       |             | Section 20.11 |
122NS*| CB_PUSH_DELEG           | OPT       | FDELG (OPT) | Section 20.5  |
123   | CB_RECALL               | OPT       | FDELG,      | Section 20.2  |
124   |                         |           | DDELG, pNFS |               |
125   |                         |           | (REQ)       |               |
126NS*| CB_RECALL_ANY           | OPT       | FDELG,      | Section 20.6  |
127   |                         |           | DDELG, pNFS |               |
128   |                         |           | (REQ)       |               |
129NS | CB_RECALL_SLOT          | REQ       |             | Section 20.8  |
130NS*| CB_RECALLABLE_OBJ_AVAIL | OPT       | DDELG, pNFS | Section 20.7  |
131   |                         |           | (REQ)       |               |
132I  | CB_SEQUENCE             | OPT       | FDELG,      | Section 20.9  |
133   |                         |           | DDELG, pNFS |               |
134   |                         |           | (REQ)       |               |
135NS*| CB_WANTS_CANCELLED      | OPT       | FDELG,      | Section 20.10 |
136   |                         |           | DDELG, pNFS |               |
137   |                         |           | (REQ)       |               |
138   +-------------------------+-----------+-------------+---------------+
139
140Implementation notes:
141
142SSV:
143* The spec claims this is mandatory, but we don't actually know of any
144  implementations, so we're ignoring it for now.  The server returns
145  NFS4ERR_ENCR_ALG_UNSUPP on EXCHANGE_ID, which should be future-proof.
146
147GSS on the backchannel:
148* Again, theoretically required but not widely implemented (in
149  particular, the current Linux client doesn't request it).  We return
150  NFS4ERR_ENCR_ALG_UNSUPP on CREATE_SESSION.
151
152DELEGPURGE:
153* mandatory only for servers that support CLAIM_DELEGATE_PREV and/or
154  CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that
155  persist across client reboots).  Thus we need not implement this for
156  now.
157
158EXCHANGE_ID:
159* implementation ids are ignored
160
161CREATE_SESSION:
162* backchannel attributes are ignored
163
164SEQUENCE:
165* no support for dynamic slot table renegotiation (optional)
166
167Nonstandard compound limitations:
168* No support for a sessions fore channel RPC compound that requires both a
169  ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
170  fail to live up to the promise we made in CREATE_SESSION fore channel
171  negotiation.
172
173See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues.
174