ffe1137ba7
Our server rejects compounds containing more than one write operation. It's unclear whether this is really permitted by the spec; with 4.0, it's possibly OK, with 4.1 (which has clearer limits on compound parameters), it's probably not OK. No client that we're aware of has ever done this, but in theory it could be useful. The source of the limitation: we need an array of iovecs to pass to the write operation. In the worst case that array of iovecs could have hundreds of elements (the maximum rwsize divided by the page size), so it's too big to put on the stack, or in each compound op. So we instead keep a single such array in the compound argument. We fill in that array at the time we decode the xdr operation. But we decode every op in the compound before executing any of them. So once we've used that array we can't decode another write. If we instead delay filling in that array till the time we actually perform the write, we can reuse it. Another option might be to switch to decoding compound ops one at a time. I considered doing that, but it has a number of other side effects, and I'd rather fix just this one problem for now. Signed-off-by: J. Bruce Fields <bfields@redhat.com>
197 lines
10 KiB
Plaintext
197 lines
10 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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- 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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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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I | 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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I | 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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| | | (REQ) | |
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NS*| CB_RECALL_ANY | OPT | FDELG, | Section 20.6 |
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| | | DDELG, pNFS | |
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| | | (REQ) | |
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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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| | | (REQ) | |
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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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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 read-like operation allowed per compound; encoding
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replies that cross page boundaries (except for read data) not handled.
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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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