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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"
6 correspondingly.
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
20 on the latest NFSv4.1 Internet Draft:
21 http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-29
23 From the many new features in NFSv4.1 the current implementation
24 focuses on the mandatory-to-implement NFSv4.1 Sessions, providing
25 "exactly once" semantics and better control and throttling of the
26 resources allocated for each client.
28 Other NFSv4.1 features, Parallel NFS operations in particular,
29 are still under development out of tree.
30 See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design
31 for more information.
33 The current implementation is intended for developers only: while it
34 does support ordinary file operations on clients we have tested against
35 (including the linux client), it is incomplete in ways which may limit
36 features unexpectedly, cause known bugs in rare cases, or cause
37 interoperability problems with future clients. Known issues:
39 - gss support is questionable: currently mounts with kerberos
40 from a linux client are possible, but we aren't really
41 conformant with the spec (for example, we don't use kerberos
42 on the backchannel correctly).
43 - no trunking support: no clients currently take advantage of
44 trunking, but this is a mandatory feature, and its use is
45 recommended to clients in a number of places. (E.g. to ensure
46 timely renewal in case an existing connection's retry timeouts
47 have gotten too long; see section 8.3 of the draft.)
48 Therefore, lack of this feature may cause future clients to
49 fail.
50 - Incomplete backchannel support: incomplete backchannel gss
51 support and no support for BACKCHANNEL_CTL mean that
52 callbacks (hence delegations and layouts) may not be
53 available and clients confused by the incomplete
54 implementation may fail.
55 - Server reboot recovery is unsupported; if the server reboots,
56 clients may fail.
57 - We do not support SSV, which provides security for shared
58 client-server state (thus preventing unauthorized tampering
59 with locks and opens, for example). It is mandatory for
60 servers to support this, though no clients use it yet.
61 - Mandatory operations which we do not support, such as
62 DESTROY_CLIENTID, FREE_STATEID, SECINFO_NO_NAME, and
63 TEST_STATEID, are not currently used by clients, but will be
64 (and the spec recommends their uses in common cases), and
65 clients should not be expected to know how to recover from the
66 case where they are not supported. This will eventually cause
67 interoperability failures.
69 In addition, some limitations are inherited from the current NFSv4
70 implementation:
72 - Incomplete delegation enforcement: if a file is renamed or
73 unlinked, a client holding a delegation may continue to
74 indefinitely allow opens of the file under the old name.
76 The table below, taken from the NFSv4.1 document, lists
77 the operations that are mandatory to implement (REQ), optional
78 (OPT), and NFSv4.0 operations that are required not to implement (MNI)
79 in minor version 1. The first column indicates the operations that
80 are not supported yet by the linux server implementation.
82 The OPTIONAL features identified and their abbreviations are as follows:
83 pNFS Parallel NFS
84 FDELG File Delegations
85 DDELG Directory Delegations
87 The following abbreviations indicate the linux server implementation status.
88 I Implemented NFSv4.1 operations.
89 NS Not Supported.
90 NS* unimplemented optional feature.
91 P pNFS features implemented out of tree.
92 PNS pNFS features that are not supported yet (out of tree).
94 Operations
96 +----------------------+------------+--------------+----------------+
97 | Operation | REQ, REC, | Feature | Definition |
98 | | OPT, or | (REQ, REC, | |
99 | | MNI | or OPT) | |
100 +----------------------+------------+--------------+----------------+
101 | ACCESS | REQ | | Section 18.1 |
102 NS | BACKCHANNEL_CTL | REQ | | Section 18.33 |
103 NS | BIND_CONN_TO_SESSION | REQ | | Section 18.34 |
104 | CLOSE | REQ | | Section 18.2 |
105 | COMMIT | REQ | | Section 18.3 |
106 | CREATE | REQ | | Section 18.4 |
107 I | CREATE_SESSION | REQ | | Section 18.36 |
108 NS*| DELEGPURGE | OPT | FDELG (REQ) | Section 18.5 |
109 | DELEGRETURN | OPT | FDELG, | Section 18.6 |
110 | | | DDELG, pNFS | |
111 | | | (REQ) | |
112 NS | DESTROY_CLIENTID | REQ | | Section 18.50 |
113 I | DESTROY_SESSION | REQ | | Section 18.37 |
114 I | EXCHANGE_ID | REQ | | Section 18.35 |
115 NS | FREE_STATEID | REQ | | Section 18.38 |
116 | GETATTR | REQ | | Section 18.7 |
117 P | GETDEVICEINFO | OPT | pNFS (REQ) | Section 18.40 |
118 P | GETDEVICELIST | OPT | pNFS (OPT) | Section 18.41 |
119 | GETFH | REQ | | Section 18.8 |
120 NS*| GET_DIR_DELEGATION | OPT | DDELG (REQ) | Section 18.39 |
121 P | LAYOUTCOMMIT | OPT | pNFS (REQ) | Section 18.42 |
122 P | LAYOUTGET | OPT | pNFS (REQ) | Section 18.43 |
123 P | LAYOUTRETURN | OPT | pNFS (REQ) | Section 18.44 |
124 | LINK | OPT | | Section 18.9 |
125 | LOCK | REQ | | Section 18.10 |
126 | LOCKT | REQ | | Section 18.11 |
127 | LOCKU | REQ | | Section 18.12 |
128 | LOOKUP | REQ | | Section 18.13 |
129 | LOOKUPP | REQ | | Section 18.14 |
130 | NVERIFY | REQ | | Section 18.15 |
131 | OPEN | REQ | | Section 18.16 |
132 NS*| OPENATTR | OPT | | Section 18.17 |
133 | OPEN_CONFIRM | MNI | | N/A |
134 | OPEN_DOWNGRADE | REQ | | Section 18.18 |
135 | PUTFH | REQ | | Section 18.19 |
136 | PUTPUBFH | REQ | | Section 18.20 |
137 | PUTROOTFH | REQ | | Section 18.21 |
138 | READ | REQ | | Section 18.22 |
139 | READDIR | REQ | | Section 18.23 |
140 | READLINK | OPT | | Section 18.24 |
141 NS | RECLAIM_COMPLETE | REQ | | Section 18.51 |
142 | RELEASE_LOCKOWNER | MNI | | N/A |
143 | REMOVE | REQ | | Section 18.25 |
144 | RENAME | REQ | | Section 18.26 |
145 | RENEW | MNI | | N/A |
146 | RESTOREFH | REQ | | Section 18.27 |
147 | SAVEFH | REQ | | Section 18.28 |
148 | SECINFO | REQ | | Section 18.29 |
149 NS | SECINFO_NO_NAME | REC | pNFS files | Section 18.45, |
150 | | | layout (REQ) | Section 13.12 |
151 I | SEQUENCE | REQ | | Section 18.46 |
152 | SETATTR | REQ | | Section 18.30 |
153 | SETCLIENTID | MNI | | N/A |
154 | SETCLIENTID_CONFIRM | MNI | | N/A |
155 NS | SET_SSV | REQ | | Section 18.47 |
156 NS | TEST_STATEID | REQ | | Section 18.48 |
157 | VERIFY | REQ | | Section 18.31 |
158 NS*| WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 |
159 | WRITE | REQ | | Section 18.32 |
161 Callback Operations
163 +-------------------------+-----------+-------------+---------------+
164 | Operation | REQ, REC, | Feature | Definition |
165 | | OPT, or | (REQ, REC, | |
166 | | MNI | or OPT) | |
167 +-------------------------+-----------+-------------+---------------+
168 | CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 |
169 P | CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 |
170 NS*| CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 |
171 P | CB_NOTIFY_DEVICEID | OPT | pNFS (OPT) | Section 20.12 |
172 NS*| CB_NOTIFY_LOCK | OPT | | Section 20.11 |
173 NS*| CB_PUSH_DELEG | OPT | FDELG (OPT) | Section 20.5 |
174 | CB_RECALL | OPT | FDELG, | Section 20.2 |
175 | | | DDELG, pNFS | |
176 | | | (REQ) | |
177 NS*| CB_RECALL_ANY | OPT | FDELG, | Section 20.6 |
178 | | | DDELG, pNFS | |
179 | | | (REQ) | |
180 NS | CB_RECALL_SLOT | REQ | | Section 20.8 |
181 NS*| CB_RECALLABLE_OBJ_AVAIL | OPT | DDELG, pNFS | Section 20.7 |
182 | | | (REQ) | |
183 I | CB_SEQUENCE | OPT | FDELG, | Section 20.9 |
184 | | | DDELG, pNFS | |
185 | | | (REQ) | |
186 NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 |
187 | | | DDELG, pNFS | |
188 | | | (REQ) | |
189 +-------------------------+-----------+-------------+---------------+
191 Implementation notes:
193 DELEGPURGE:
194 * mandatory only for servers that support CLAIM_DELEGATE_PREV and/or
195 CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that
196 persist across client reboots). Thus we need not implement this for
197 now.
199 EXCHANGE_ID:
200 * only SP4_NONE state protection supported
201 * implementation ids are ignored
203 CREATE_SESSION:
204 * backchannel attributes are ignored
205 * backchannel security parameters are ignored
207 SEQUENCE:
208 * no support for dynamic slot table renegotiation (optional)
210 nfsv4.1 COMPOUND rules:
211 The following cases aren't supported yet:
212 * Enforcing of NFS4ERR_NOT_ONLY_OP for: BIND_CONN_TO_SESSION, CREATE_SESSION,
213 DESTROY_CLIENTID, DESTROY_SESSION, EXCHANGE_ID.
214 * DESTROY_SESSION MUST be the final operation in the COMPOUND request.
216 Nonstandard compound limitations:
217 * No support for a sessions fore channel RPC compound that requires both a
218 ca_maxrequestsize request and a ca_maxresponsesize reply, so we may
219 fail to live up to the promise we made in CREATE_SESSION fore channel
220 negotiation.
221 * No more than one IO operation (read, write, readdir) allowed per
222 compound.