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 disabled by default. 9It can be enabled 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. Use your user-mode 12nfs-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 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 27Other NFSv4.1 features, Parallel NFS operations in particular, 28are still under development out of tree. 29See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design 30for more information. 31 32The current implementation is intended for developers only: while it 33does support ordinary file operations on clients we have tested against 34(including the linux client), it is incomplete in ways which may limit 35features unexpectedly, cause known bugs in rare cases, or cause 36interoperability 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 - Incomplete backchannel support: incomplete backchannel gss 43 support and no support for BACKCHANNEL_CTL mean that 44 callbacks (hence delegations and layouts) may not be 45 available and clients confused by the incomplete 46 implementation may fail. 47 - We do not support SSV, which provides security for shared 48 client-server state (thus preventing unauthorized tampering 49 with locks and opens, for example). It is mandatory for 50 servers to support this, though no clients use it yet. 51 - Mandatory operations which we do not support, such as 52 DESTROY_CLIENTID, are not currently used by clients, but will be 53 (and the spec recommends their uses in common cases), and 54 clients should not be expected to know how to recover from the 55 case where they are not supported. This will eventually cause 56 interoperability failures. 57 58In addition, some limitations are inherited from the current NFSv4 59implementation: 60 61 - Incomplete delegation enforcement: if a file is renamed or 62 unlinked by a local process, a client holding a delegation may 63 continue to indefinitely allow opens of the file under the old 64 name. 65 66The table below, taken from the NFSv4.1 document, lists 67the operations that are mandatory to implement (REQ), optional 68(OPT), and NFSv4.0 operations that are required not to implement (MNI) 69in minor version 1. The first column indicates the operations that 70are not supported yet by the linux server implementation. 71 72The OPTIONAL features identified and their abbreviations are as follows: 73 pNFS Parallel NFS 74 FDELG File Delegations 75 DDELG Directory Delegations 76 77The following abbreviations indicate the linux server implementation status. 78 I Implemented NFSv4.1 operations. 79 NS Not Supported. 80 NS* unimplemented optional feature. 81 P pNFS features implemented out of tree. 82 PNS pNFS features that are not supported yet (out of tree). 83 84Operations 85 86 +----------------------+------------+--------------+----------------+ 87 | Operation | REQ, REC, | Feature | Definition | 88 | | OPT, or | (REQ, REC, | | 89 | | MNI | or OPT) | | 90 +----------------------+------------+--------------+----------------+ 91 | ACCESS | REQ | | Section 18.1 | 92NS | BACKCHANNEL_CTL | REQ | | Section 18.33 | 93I | BIND_CONN_TO_SESSION | REQ | | Section 18.34 | 94 | CLOSE | REQ | | Section 18.2 | 95 | COMMIT | REQ | | Section 18.3 | 96 | CREATE | REQ | | Section 18.4 | 97I | CREATE_SESSION | REQ | | Section 18.36 | 98NS*| DELEGPURGE | OPT | FDELG (REQ) | Section 18.5 | 99 | DELEGRETURN | OPT | FDELG, | Section 18.6 | 100 | | | DDELG, pNFS | | 101 | | | (REQ) | | 102NS | DESTROY_CLIENTID | REQ | | Section 18.50 | 103I | DESTROY_SESSION | REQ | | Section 18.37 | 104I | EXCHANGE_ID | REQ | | Section 18.35 | 105I | FREE_STATEID | REQ | | Section 18.38 | 106 | GETATTR | REQ | | Section 18.7 | 107P | GETDEVICEINFO | OPT | pNFS (REQ) | Section 18.40 | 108P | GETDEVICELIST | OPT | pNFS (OPT) | Section 18.41 | 109 | GETFH | REQ | | Section 18.8 | 110NS*| GET_DIR_DELEGATION | OPT | DDELG (REQ) | Section 18.39 | 111P | LAYOUTCOMMIT | OPT | pNFS (REQ) | Section 18.42 | 112P | LAYOUTGET | OPT | pNFS (REQ) | Section 18.43 | 113P | LAYOUTRETURN | OPT | pNFS (REQ) | Section 18.44 | 114 | LINK | OPT | | Section 18.9 | 115 | LOCK | REQ | | Section 18.10 | 116 | LOCKT | REQ | | Section 18.11 | 117 | LOCKU | REQ | | Section 18.12 | 118 | LOOKUP | REQ | | Section 18.13 | 119 | LOOKUPP | REQ | | Section 18.14 | 120 | NVERIFY | REQ | | Section 18.15 | 121 | OPEN | REQ | | Section 18.16 | 122NS*| OPENATTR | OPT | | Section 18.17 | 123 | OPEN_CONFIRM | MNI | | N/A | 124 | OPEN_DOWNGRADE | REQ | | Section 18.18 | 125 | PUTFH | REQ | | Section 18.19 | 126 | PUTPUBFH | REQ | | Section 18.20 | 127 | PUTROOTFH | REQ | | Section 18.21 | 128 | READ | REQ | | Section 18.22 | 129 | READDIR | REQ | | Section 18.23 | 130 | READLINK | OPT | | Section 18.24 | 131 | RECLAIM_COMPLETE | REQ | | Section 18.51 | 132 | RELEASE_LOCKOWNER | MNI | | N/A | 133 | REMOVE | REQ | | Section 18.25 | 134 | RENAME | REQ | | Section 18.26 | 135 | RENEW | MNI | | N/A | 136 | RESTOREFH | REQ | | Section 18.27 | 137 | SAVEFH | REQ | | Section 18.28 | 138 | SECINFO | REQ | | Section 18.29 | 139I | SECINFO_NO_NAME | REC | pNFS files | Section 18.45, | 140 | | | layout (REQ) | Section 13.12 | 141I | SEQUENCE | REQ | | Section 18.46 | 142 | SETATTR | REQ | | Section 18.30 | 143 | SETCLIENTID | MNI | | N/A | 144 | SETCLIENTID_CONFIRM | MNI | | N/A | 145NS | SET_SSV | REQ | | Section 18.47 | 146I | TEST_STATEID | REQ | | Section 18.48 | 147 | VERIFY | REQ | | Section 18.31 | 148NS*| WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 | 149 | WRITE | REQ | | Section 18.32 | 150 151Callback Operations 152 153 +-------------------------+-----------+-------------+---------------+ 154 | Operation | REQ, REC, | Feature | Definition | 155 | | OPT, or | (REQ, REC, | | 156 | | MNI | or OPT) | | 157 +-------------------------+-----------+-------------+---------------+ 158 | CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 | 159P | CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 | 160NS*| CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 | 161P | CB_NOTIFY_DEVICEID | OPT | pNFS (OPT) | Section 20.12 | 162NS*| CB_NOTIFY_LOCK | OPT | | Section 20.11 | 163NS*| CB_PUSH_DELEG | OPT | FDELG (OPT) | Section 20.5 | 164 | CB_RECALL | OPT | FDELG, | Section 20.2 | 165 | | | DDELG, pNFS | | 166 | | | (REQ) | | 167NS*| CB_RECALL_ANY | OPT | FDELG, | Section 20.6 | 168 | | | DDELG, pNFS | | 169 | | | (REQ) | | 170NS | CB_RECALL_SLOT | REQ | | Section 20.8 | 171NS*| CB_RECALLABLE_OBJ_AVAIL | OPT | DDELG, pNFS | Section 20.7 | 172 | | | (REQ) | | 173I | CB_SEQUENCE | OPT | FDELG, | Section 20.9 | 174 | | | DDELG, pNFS | | 175 | | | (REQ) | | 176NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 | 177 | | | DDELG, pNFS | | 178 | | | (REQ) | | 179 +-------------------------+-----------+-------------+---------------+ 180 181Implementation notes: 182 183DELEGPURGE: 184* mandatory only for servers that support CLAIM_DELEGATE_PREV and/or 185 CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that 186 persist across client reboots). Thus we need not implement this for 187 now. 188 189EXCHANGE_ID: 190* only SP4_NONE state protection supported 191* implementation ids are ignored 192 193CREATE_SESSION: 194* backchannel attributes are ignored 195* backchannel security parameters are ignored 196 197SEQUENCE: 198* no support for dynamic slot table renegotiation (optional) 199 200Nonstandard compound limitations: 201* No support for a sessions fore channel RPC compound that requires both a 202 ca_maxrequestsize request and a ca_maxresponsesize reply, so we may 203 fail to live up to the promise we made in CREATE_SESSION fore channel 204 negotiation. 205* No more than one IO operation (read, write, readdir) allowed per 206 compound. 207 208See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues. 209