| NFSv4.1 Server Implementation |
| |
| Server support for minorversion 1 can be controlled using the |
| /proc/fs/nfsd/versions control file. The string output returned |
| by reading this file will contain either "+4.1" or "-4.1" |
| correspondingly. |
| |
| Currently, server support for minorversion 1 is disabled by default. |
| It can be enabled at run time by writing the string "+4.1" to |
| the /proc/fs/nfsd/versions control file. Note that to write this |
| control file, the nfsd service must be taken down. Use your user-mode |
| nfs-utils to set this up; see rpc.nfsd(8) |
| |
| (Warning: older servers will interpret "+4.1" and "-4.1" as "+4" and |
| "-4", respectively. Therefore, code meant to work on both new and old |
| kernels must turn 4.1 on or off *before* turning support for version 4 |
| on or off; rpc.nfsd does this correctly.) |
| |
| The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based |
| on RFC 5661. |
| |
| From the many new features in NFSv4.1 the current implementation |
| focuses on the mandatory-to-implement NFSv4.1 Sessions, providing |
| "exactly once" semantics and better control and throttling of the |
| resources allocated for each client. |
| |
| Other NFSv4.1 features, Parallel NFS operations in particular, |
| are still under development out of tree. |
| See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design |
| for more information. |
| |
| The current implementation is intended for developers only: while it |
| does support ordinary file operations on clients we have tested against |
| (including the linux client), it is incomplete in ways which may limit |
| features unexpectedly, cause known bugs in rare cases, or cause |
| interoperability problems with future clients. Known issues: |
| |
| - gss support is questionable: currently mounts with kerberos |
| from a linux client are possible, but we aren't really |
| conformant with the spec (for example, we don't use kerberos |
| on the backchannel correctly). |
| - Incomplete backchannel support: incomplete backchannel gss |
| support and no support for BACKCHANNEL_CTL mean that |
| callbacks (hence delegations and layouts) may not be |
| available and clients confused by the incomplete |
| implementation may fail. |
| - We do not support SSV, which provides security for shared |
| client-server state (thus preventing unauthorized tampering |
| with locks and opens, for example). It is mandatory for |
| servers to support this, though no clients use it yet. |
| - Mandatory operations which we do not support, such as |
| DESTROY_CLIENTID, are not currently used by clients, but will be |
| (and the spec recommends their uses in common cases), and |
| clients should not be expected to know how to recover from the |
| case where they are not supported. This will eventually cause |
| interoperability failures. |
| |
| In addition, some limitations are inherited from the current NFSv4 |
| implementation: |
| |
| - Incomplete delegation enforcement: if a file is renamed or |
| unlinked by a local process, a client holding a delegation may |
| continue to indefinitely allow opens of the file under the old |
| name. |
| |
| The table below, taken from the NFSv4.1 document, lists |
| the operations that are mandatory to implement (REQ), optional |
| (OPT), and NFSv4.0 operations that are required not to implement (MNI) |
| in minor version 1. The first column indicates the operations that |
| are not supported yet by the linux server implementation. |
| |
| The OPTIONAL features identified and their abbreviations are as follows: |
| pNFS Parallel NFS |
| FDELG File Delegations |
| DDELG Directory Delegations |
| |
| The following abbreviations indicate the linux server implementation status. |
| I Implemented NFSv4.1 operations. |
| NS Not Supported. |
| NS* unimplemented optional feature. |
| P pNFS features implemented out of tree. |
| PNS pNFS features that are not supported yet (out of tree). |
| |
| Operations |
| |
| +----------------------+------------+--------------+----------------+ |
| | Operation | REQ, REC, | Feature | Definition | |
| | | OPT, or | (REQ, REC, | | |
| | | MNI | or OPT) | | |
| +----------------------+------------+--------------+----------------+ |
| | ACCESS | REQ | | Section 18.1 | |
| NS | BACKCHANNEL_CTL | REQ | | Section 18.33 | |
| I | BIND_CONN_TO_SESSION | REQ | | Section 18.34 | |
| | CLOSE | REQ | | Section 18.2 | |
| | COMMIT | REQ | | Section 18.3 | |
| | CREATE | REQ | | Section 18.4 | |
| I | CREATE_SESSION | REQ | | Section 18.36 | |
| NS*| DELEGPURGE | OPT | FDELG (REQ) | Section 18.5 | |
| | DELEGRETURN | OPT | FDELG, | Section 18.6 | |
| | | | DDELG, pNFS | | |
| | | | (REQ) | | |
| NS | DESTROY_CLIENTID | REQ | | Section 18.50 | |
| I | DESTROY_SESSION | REQ | | Section 18.37 | |
| I | EXCHANGE_ID | REQ | | Section 18.35 | |
| I | FREE_STATEID | REQ | | Section 18.38 | |
| | GETATTR | REQ | | Section 18.7 | |
| P | GETDEVICEINFO | OPT | pNFS (REQ) | Section 18.40 | |
| P | GETDEVICELIST | OPT | pNFS (OPT) | Section 18.41 | |
| | GETFH | REQ | | Section 18.8 | |
| NS*| GET_DIR_DELEGATION | OPT | DDELG (REQ) | Section 18.39 | |
| P | LAYOUTCOMMIT | OPT | pNFS (REQ) | Section 18.42 | |
| P | LAYOUTGET | OPT | pNFS (REQ) | Section 18.43 | |
| P | LAYOUTRETURN | OPT | pNFS (REQ) | Section 18.44 | |
| | LINK | OPT | | Section 18.9 | |
| | LOCK | REQ | | Section 18.10 | |
| | LOCKT | REQ | | Section 18.11 | |
| | LOCKU | REQ | | Section 18.12 | |
| | LOOKUP | REQ | | Section 18.13 | |
| | LOOKUPP | REQ | | Section 18.14 | |
| | NVERIFY | REQ | | Section 18.15 | |
| | OPEN | REQ | | Section 18.16 | |
| NS*| OPENATTR | OPT | | Section 18.17 | |
| | OPEN_CONFIRM | MNI | | N/A | |
| | OPEN_DOWNGRADE | REQ | | Section 18.18 | |
| | PUTFH | REQ | | Section 18.19 | |
| | PUTPUBFH | REQ | | Section 18.20 | |
| | PUTROOTFH | REQ | | Section 18.21 | |
| | READ | REQ | | Section 18.22 | |
| | READDIR | REQ | | Section 18.23 | |
| | READLINK | OPT | | Section 18.24 | |
| | RECLAIM_COMPLETE | REQ | | Section 18.51 | |
| | RELEASE_LOCKOWNER | MNI | | N/A | |
| | REMOVE | REQ | | Section 18.25 | |
| | RENAME | REQ | | Section 18.26 | |
| | RENEW | MNI | | N/A | |
| | RESTOREFH | REQ | | Section 18.27 | |
| | SAVEFH | REQ | | Section 18.28 | |
| | SECINFO | REQ | | Section 18.29 | |
| I | SECINFO_NO_NAME | REC | pNFS files | Section 18.45, | |
| | | | layout (REQ) | Section 13.12 | |
| I | SEQUENCE | REQ | | Section 18.46 | |
| | SETATTR | REQ | | Section 18.30 | |
| | SETCLIENTID | MNI | | N/A | |
| | SETCLIENTID_CONFIRM | MNI | | N/A | |
| NS | SET_SSV | REQ | | Section 18.47 | |
| I | TEST_STATEID | REQ | | Section 18.48 | |
| | VERIFY | REQ | | Section 18.31 | |
| NS*| WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 | |
| | WRITE | REQ | | Section 18.32 | |
| |
| Callback Operations |
| |
| +-------------------------+-----------+-------------+---------------+ |
| | Operation | REQ, REC, | Feature | Definition | |
| | | OPT, or | (REQ, REC, | | |
| | | MNI | or OPT) | | |
| +-------------------------+-----------+-------------+---------------+ |
| | CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 | |
| P | CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 | |
| NS*| CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 | |
| P | CB_NOTIFY_DEVICEID | OPT | pNFS (OPT) | Section 20.12 | |
| NS*| CB_NOTIFY_LOCK | OPT | | Section 20.11 | |
| NS*| CB_PUSH_DELEG | OPT | FDELG (OPT) | Section 20.5 | |
| | CB_RECALL | OPT | FDELG, | Section 20.2 | |
| | | | DDELG, pNFS | | |
| | | | (REQ) | | |
| NS*| CB_RECALL_ANY | OPT | FDELG, | Section 20.6 | |
| | | | DDELG, pNFS | | |
| | | | (REQ) | | |
| NS | CB_RECALL_SLOT | REQ | | Section 20.8 | |
| NS*| CB_RECALLABLE_OBJ_AVAIL | OPT | DDELG, pNFS | Section 20.7 | |
| | | | (REQ) | | |
| I | CB_SEQUENCE | OPT | FDELG, | Section 20.9 | |
| | | | DDELG, pNFS | | |
| | | | (REQ) | | |
| NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 | |
| | | | DDELG, pNFS | | |
| | | | (REQ) | | |
| +-------------------------+-----------+-------------+---------------+ |
| |
| Implementation notes: |
| |
| DELEGPURGE: |
| * mandatory only for servers that support CLAIM_DELEGATE_PREV and/or |
| CLAIM_DELEG_PREV_FH (which allows clients to keep delegations that |
| persist across client reboots). Thus we need not implement this for |
| now. |
| |
| EXCHANGE_ID: |
| * only SP4_NONE state protection supported |
| * implementation ids are ignored |
| |
| CREATE_SESSION: |
| * backchannel attributes are ignored |
| * backchannel security parameters are ignored |
| |
| SEQUENCE: |
| * no support for dynamic slot table renegotiation (optional) |
| |
| Nonstandard compound limitations: |
| * No support for a sessions fore channel RPC compound that requires both a |
| ca_maxrequestsize request and a ca_maxresponsesize reply, so we may |
| fail to live up to the promise we made in CREATE_SESSION fore channel |
| negotiation. |
| * No more than one IO operation (read, write, readdir) allowed per |
| compound. |
| |
| See also http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues. |