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