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Documentation / filesystems / nfs / nfs41-server.txt




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Based on kernel version 3.13. Page generated on 2014-01-20 22:02 EST.

1	NFSv4.1 Server Implementation
2	
3	Server support for minorversion 1 can be controlled using the
4	/proc/fs/nfsd/versions control file.  The string output returned
5	by reading this file will contain either "+4.1" or "-4.1"
6	correspondingly.
7	
8	Currently, server support for minorversion 1 is disabled by default.
9	It can be enabled at run time by writing the string "+4.1" to
10	the /proc/fs/nfsd/versions control file.  Note that to write this
11	control file, the nfsd service must be taken down.  Use your user-mode
12	nfs-utils to set this up; 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
16	kernels must turn 4.1 on or off *before* turning support for version 4
17	on or off; rpc.nfsd does this correctly.)
18	
19	The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based
20	on RFC 5661.
21	
22	From the many new features in NFSv4.1 the current implementation
23	focuses on the mandatory-to-implement NFSv4.1 Sessions, providing
24	"exactly once" semantics and better control and throttling of the
25	resources allocated for each client.
26	
27	Other NFSv4.1 features, Parallel NFS operations in particular,
28	are still under development out of tree.
29	See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design
30	for more information.
31	
32	The current implementation is intended for developers only: while it
33	does support ordinary file operations on clients we have tested against
34	(including the linux client), it is incomplete in ways which may limit
35	features unexpectedly, cause known bugs in rare cases, or cause
36	interoperability problems with future clients.  Known issues:
37	
38		- gss support is questionable: currently mounts with kerberos
39		  from a linux client are possible, but we aren't really
40		  conformant with the spec (for example, we don't use kerberos
41		  on the backchannel correctly).
42		- We do not support SSV, which provides security for shared
43		  client-server state (thus preventing unauthorized tampering
44		  with locks and opens, for example).  It is mandatory for
45		  servers to support this, though no clients use it yet.
46	
47	In addition, some limitations are inherited from the current NFSv4
48	implementation:
49	
50		- Incomplete delegation enforcement: if a file is renamed or
51		  unlinked by a local process, a client holding a delegation may
52		  continue to indefinitely allow opens of the file under the old
53		  name.
54	
55	The table below, taken from the NFSv4.1 document, lists
56	the operations that are mandatory to implement (REQ), optional
57	(OPT), and NFSv4.0 operations that are required not to implement (MNI)
58	in minor version 1.  The first column indicates the operations that
59	are not supported yet by the linux server implementation.
60	
61	The OPTIONAL features identified and their abbreviations are as follows:
62		pNFS	Parallel NFS
63		FDELG	File Delegations
64		DDELG	Directory Delegations
65	
66	The following abbreviations indicate the linux server implementation status.
67		I	Implemented NFSv4.1 operations.
68		NS	Not Supported.
69		NS*	unimplemented optional feature.
70		P	pNFS features implemented out of tree.
71		PNS	pNFS features that are not supported yet (out of tree).
72	
73	Operations
74	
75	   +----------------------+------------+--------------+----------------+
76	   | Operation            | REQ, REC,  | Feature      | Definition     |
77	   |                      | OPT, or    | (REQ, REC,   |                |
78	   |                      | MNI        | or OPT)      |                |
79	   +----------------------+------------+--------------+----------------+
80	   | ACCESS               | REQ        |              | Section 18.1   |
81	I  | BACKCHANNEL_CTL      | REQ        |              | Section 18.33  |
82	I  | BIND_CONN_TO_SESSION | REQ        |              | Section 18.34  |
83	   | CLOSE                | REQ        |              | Section 18.2   |
84	   | COMMIT               | REQ        |              | Section 18.3   |
85	   | CREATE               | REQ        |              | Section 18.4   |
86	I  | CREATE_SESSION       | REQ        |              | Section 18.36  |
87	NS*| DELEGPURGE           | OPT        | FDELG (REQ)  | Section 18.5   |
88	   | DELEGRETURN          | OPT        | FDELG,       | Section 18.6   |
89	   |                      |            | DDELG, pNFS  |                |
90	   |                      |            | (REQ)        |                |
91	I  | DESTROY_CLIENTID     | REQ        |              | Section 18.50  |
92	I  | DESTROY_SESSION      | REQ        |              | Section 18.37  |
93	I  | EXCHANGE_ID          | REQ        |              | Section 18.35  |
94	I  | FREE_STATEID         | REQ        |              | Section 18.38  |
95	   | GETATTR              | REQ        |              | Section 18.7   |
96	P  | GETDEVICEINFO        | OPT        | pNFS (REQ)   | Section 18.40  |
97	P  | GETDEVICELIST        | OPT        | pNFS (OPT)   | Section 18.41  |
98	   | GETFH                | REQ        |              | Section 18.8   |
99	NS*| GET_DIR_DELEGATION   | OPT        | DDELG (REQ)  | Section 18.39  |
100	P  | LAYOUTCOMMIT         | OPT        | pNFS (REQ)   | Section 18.42  |
101	P  | LAYOUTGET            | OPT        | pNFS (REQ)   | Section 18.43  |
102	P  | LAYOUTRETURN         | OPT        | pNFS (REQ)   | Section 18.44  |
103	   | LINK                 | OPT        |              | Section 18.9   |
104	   | LOCK                 | REQ        |              | Section 18.10  |
105	   | LOCKT                | REQ        |              | Section 18.11  |
106	   | LOCKU                | REQ        |              | Section 18.12  |
107	   | LOOKUP               | REQ        |              | Section 18.13  |
108	   | LOOKUPP              | REQ        |              | Section 18.14  |
109	   | NVERIFY              | REQ        |              | Section 18.15  |
110	   | OPEN                 | REQ        |              | Section 18.16  |
111	NS*| OPENATTR             | OPT        |              | Section 18.17  |
112	   | OPEN_CONFIRM         | MNI        |              | N/A            |
113	   | OPEN_DOWNGRADE       | REQ        |              | Section 18.18  |
114	   | PUTFH                | REQ        |              | Section 18.19  |
115	   | PUTPUBFH             | REQ        |              | Section 18.20  |
116	   | PUTROOTFH            | REQ        |              | Section 18.21  |
117	   | READ                 | REQ        |              | Section 18.22  |
118	   | READDIR              | REQ        |              | Section 18.23  |
119	   | READLINK             | OPT        |              | Section 18.24  |
120	   | RECLAIM_COMPLETE     | REQ        |              | Section 18.51  |
121	   | RELEASE_LOCKOWNER    | MNI        |              | N/A            |
122	   | REMOVE               | REQ        |              | Section 18.25  |
123	   | RENAME               | REQ        |              | Section 18.26  |
124	   | RENEW                | MNI        |              | N/A            |
125	   | RESTOREFH            | REQ        |              | Section 18.27  |
126	   | SAVEFH               | REQ        |              | Section 18.28  |
127	   | SECINFO              | REQ        |              | Section 18.29  |
128	I  | SECINFO_NO_NAME      | REC        | pNFS files   | Section 18.45, |
129	   |                      |            | layout (REQ) | Section 13.12  |
130	I  | SEQUENCE             | REQ        |              | Section 18.46  |
131	   | SETATTR              | REQ        |              | Section 18.30  |
132	   | SETCLIENTID          | MNI        |              | N/A            |
133	   | SETCLIENTID_CONFIRM  | MNI        |              | N/A            |
134	NS | SET_SSV              | REQ        |              | Section 18.47  |
135	I  | TEST_STATEID         | REQ        |              | Section 18.48  |
136	   | VERIFY               | REQ        |              | Section 18.31  |
137	NS*| WANT_DELEGATION      | OPT        | FDELG (OPT)  | Section 18.49  |
138	   | WRITE                | REQ        |              | Section 18.32  |
139	
140	Callback Operations
141	
142	   +-------------------------+-----------+-------------+---------------+
143	   | Operation               | REQ, REC, | Feature     | Definition    |
144	   |                         | OPT, or   | (REQ, REC,  |               |
145	   |                         | MNI       | or OPT)     |               |
146	   +-------------------------+-----------+-------------+---------------+
147	   | CB_GETATTR              | OPT       | FDELG (REQ) | Section 20.1  |
148	P  | CB_LAYOUTRECALL         | OPT       | pNFS (REQ)  | Section 20.3  |
149	NS*| CB_NOTIFY               | OPT       | DDELG (REQ) | Section 20.4  |
150	P  | CB_NOTIFY_DEVICEID      | OPT       | pNFS (OPT)  | Section 20.12 |
151	NS*| CB_NOTIFY_LOCK          | OPT       |             | Section 20.11 |
152	NS*| CB_PUSH_DELEG           | OPT       | FDELG (OPT) | Section 20.5  |
153	   | CB_RECALL               | OPT       | FDELG,      | Section 20.2  |
154	   |                         |           | DDELG, pNFS |               |
155	   |                         |           | (REQ)       |               |
156	NS*| CB_RECALL_ANY           | OPT       | FDELG,      | Section 20.6  |
157	   |                         |           | DDELG, pNFS |               |
158	   |                         |           | (REQ)       |               |
159	NS | CB_RECALL_SLOT          | REQ       |             | Section 20.8  |
160	NS*| CB_RECALLABLE_OBJ_AVAIL | OPT       | DDELG, pNFS | Section 20.7  |
161	   |                         |           | (REQ)       |               |
162	I  | CB_SEQUENCE             | OPT       | FDELG,      | Section 20.9  |
163	   |                         |           | DDELG, pNFS |               |
164	   |                         |           | (REQ)       |               |
165	NS*| CB_WANTS_CANCELLED      | OPT       | FDELG,      | Section 20.10 |
166	   |                         |           | DDELG, pNFS |               |
167	   |                         |           | (REQ)       |               |
168	   +-------------------------+-----------+-------------+---------------+
169	
170	Implementation notes:
171	
172	DELEGPURGE:
173	* mandatory only for servers that support CLAIM_DELEGATE_PREV and/or
174	  CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that
175	  persist across client reboots).  Thus we need not implement this for
176	  now.
177	
178	EXCHANGE_ID:
179	* only SP4_NONE state protection supported
180	* implementation ids are ignored
181	
182	CREATE_SESSION:
183	* backchannel attributes are ignored
184	
185	SEQUENCE:
186	* no support for dynamic slot table renegotiation (optional)
187	
188	Nonstandard compound limitations:
189	* No support for a sessions fore channel RPC compound that requires both a
190	  ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
191	  fail to live up to the promise we made in CREATE_SESSION fore channel
192	  negotiation.
193	* No more than one read-like operation allowed per compound; encoding
194	  replies that cross page boundaries (except for read data) not handled.
195	
196	See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues.
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