1 NFSv4.1 Server Implementation
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"
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)
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.)
19 The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based
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.
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
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:
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 - Mandatory operations which we do not support, such as
47 DESTROY_CLIENTID, are not currently used by clients, but will be
48 (and the spec recommends their uses in common cases), and
49 clients should not be expected to know how to recover from the
50 case where they are not supported. This will eventually cause
51 interoperability failures.
53 In addition, some limitations are inherited from the current NFSv4
56 - Incomplete delegation enforcement: if a file is renamed or
57 unlinked by a local process, a client holding a delegation may
58 continue to indefinitely allow opens of the file under the old
61 The table below, taken from the NFSv4.1 document, lists
62 the operations that are mandatory to implement (REQ), optional
63 (OPT), and NFSv4.0 operations that are required not to implement (MNI)
64 in minor version 1. The first column indicates the operations that
65 are not supported yet by the linux server implementation.
67 The OPTIONAL features identified and their abbreviations are as follows:
69 FDELG File Delegations
70 DDELG Directory Delegations
72 The following abbreviations indicate the linux server implementation status.
73 I Implemented NFSv4.1 operations.
75 NS* unimplemented optional feature.
76 P pNFS features implemented out of tree.
77 PNS pNFS features that are not supported yet (out of tree).
81 +----------------------+------------+--------------+----------------+
82 | Operation | REQ, REC, | Feature | Definition |
83 | | OPT, or | (REQ, REC, | |
85 +----------------------+------------+--------------+----------------+
86 | ACCESS | REQ | | Section 18.1 |
87 I | BACKCHANNEL_CTL | REQ | | Section 18.33 |
88 I | BIND_CONN_TO_SESSION | REQ | | Section 18.34 |
89 | CLOSE | REQ | | Section 18.2 |
90 | COMMIT | REQ | | Section 18.3 |
91 | CREATE | REQ | | Section 18.4 |
92 I | CREATE_SESSION | REQ | | Section 18.36 |
93 NS*| DELEGPURGE | OPT | FDELG (REQ) | Section 18.5 |
94 | DELEGRETURN | OPT | FDELG, | Section 18.6 |
97 NS | DESTROY_CLIENTID | REQ | | Section 18.50 |
98 I | DESTROY_SESSION | REQ | | Section 18.37 |
99 I | EXCHANGE_ID | REQ | | Section 18.35 |
100 I | FREE_STATEID | REQ | | Section 18.38 |
101 | GETATTR | REQ | | Section 18.7 |
102 P | GETDEVICEINFO | OPT | pNFS (REQ) | Section 18.40 |
103 P | GETDEVICELIST | OPT | pNFS (OPT) | Section 18.41 |
104 | GETFH | REQ | | Section 18.8 |
105 NS*| GET_DIR_DELEGATION | OPT | DDELG (REQ) | Section 18.39 |
106 P | LAYOUTCOMMIT | OPT | pNFS (REQ) | Section 18.42 |
107 P | LAYOUTGET | OPT | pNFS (REQ) | Section 18.43 |
108 P | LAYOUTRETURN | OPT | pNFS (REQ) | Section 18.44 |
109 | LINK | OPT | | Section 18.9 |
110 | LOCK | REQ | | Section 18.10 |
111 | LOCKT | REQ | | Section 18.11 |
112 | LOCKU | REQ | | Section 18.12 |
113 | LOOKUP | REQ | | Section 18.13 |
114 | LOOKUPP | REQ | | Section 18.14 |
115 | NVERIFY | REQ | | Section 18.15 |
116 | OPEN | REQ | | Section 18.16 |
117 NS*| OPENATTR | OPT | | Section 18.17 |
118 | OPEN_CONFIRM | MNI | | N/A |
119 | OPEN_DOWNGRADE | REQ | | Section 18.18 |
120 | PUTFH | REQ | | Section 18.19 |
121 | PUTPUBFH | REQ | | Section 18.20 |
122 | PUTROOTFH | REQ | | Section 18.21 |
123 | READ | REQ | | Section 18.22 |
124 | READDIR | REQ | | Section 18.23 |
125 | READLINK | OPT | | Section 18.24 |
126 | RECLAIM_COMPLETE | REQ | | Section 18.51 |
127 | RELEASE_LOCKOWNER | MNI | | N/A |
128 | REMOVE | REQ | | Section 18.25 |
129 | RENAME | REQ | | Section 18.26 |
130 | RENEW | MNI | | N/A |
131 | RESTOREFH | REQ | | Section 18.27 |
132 | SAVEFH | REQ | | Section 18.28 |
133 | SECINFO | REQ | | Section 18.29 |
134 I | SECINFO_NO_NAME | REC | pNFS files | Section 18.45, |
135 | | | layout (REQ) | Section 13.12 |
136 I | SEQUENCE | REQ | | Section 18.46 |
137 | SETATTR | REQ | | Section 18.30 |
138 | SETCLIENTID | MNI | | N/A |
139 | SETCLIENTID_CONFIRM | MNI | | N/A |
140 NS | SET_SSV | REQ | | Section 18.47 |
141 I | TEST_STATEID | REQ | | Section 18.48 |
142 | VERIFY | REQ | | Section 18.31 |
143 NS*| WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 |
144 | WRITE | REQ | | Section 18.32 |
148 +-------------------------+-----------+-------------+---------------+
149 | Operation | REQ, REC, | Feature | Definition |
150 | | OPT, or | (REQ, REC, | |
151 | | MNI | or OPT) | |
152 +-------------------------+-----------+-------------+---------------+
153 | CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 |
154 P | CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 |
155 NS*| CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 |
156 P | CB_NOTIFY_DEVICEID | OPT | pNFS (OPT) | Section 20.12 |
157 NS*| CB_NOTIFY_LOCK | OPT | | Section 20.11 |
158 NS*| CB_PUSH_DELEG | OPT | FDELG (OPT) | Section 20.5 |
159 | CB_RECALL | OPT | FDELG, | Section 20.2 |
160 | | | DDELG, pNFS | |
162 NS*| CB_RECALL_ANY | OPT | FDELG, | Section 20.6 |
163 | | | DDELG, pNFS | |
165 NS | CB_RECALL_SLOT | REQ | | Section 20.8 |
166 NS*| CB_RECALLABLE_OBJ_AVAIL | OPT | DDELG, pNFS | Section 20.7 |
168 I | CB_SEQUENCE | OPT | FDELG, | Section 20.9 |
169 | | | DDELG, pNFS | |
171 NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 |
172 | | | DDELG, pNFS | |
174 +-------------------------+-----------+-------------+---------------+
176 Implementation notes:
179 * mandatory only for servers that support CLAIM_DELEGATE_PREV and/or
180 CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that
181 persist across client reboots). Thus we need not implement this for
185 * only SP4_NONE state protection supported
186 * implementation ids are ignored
189 * backchannel attributes are ignored
190 * backchannel security parameters are ignored
193 * no support for dynamic slot table renegotiation (optional)
195 Nonstandard compound limitations:
196 * No support for a sessions fore channel RPC compound that requires both a
197 ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
198 fail to live up to the promise we made in CREATE_SESSION fore channel
200 * No more than one IO operation (read, write, readdir) allowed per
203 See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues.