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RFC 7862


Network File System (NFS) Version 4 Minor Version 2 Protocol

Part 6 of 6, p. 98 to 104
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16.  NFSv4.2 Callback Operations

16.1.  Operation 15: CB_OFFLOAD - Report the results of an asynchronous

16.1.1.  ARGUMENT


   struct write_response4 {
           stateid4        wr_callback_id<1>;
           length4         wr_count;
           stable_how4     wr_committed;
           verifier4       wr_writeverf;

   union offload_info4 switch (nfsstat4 coa_status) {
   case NFS4_OK:
           write_response4 coa_resok4;
           length4         coa_bytes_copied;

   struct CB_OFFLOAD4args {
           nfs_fh4         coa_fh;
           stateid4        coa_stateid;
           offload_info4   coa_offload_info;


16.1.2.  RESULT


   struct CB_OFFLOAD4res {
           nfsstat4        cor_status;


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   CB_OFFLOAD is used to report to the client the results of an
   asynchronous operation, e.g., server-side COPY or WRITE_SAME.  The
   coa_fh and coa_stateid identify the transaction, and the coa_status
   indicates success or failure.  The coa_resok4.wr_callback_id MUST NOT
   be set.  If the transaction failed, then the coa_bytes_copied
   contains the number of bytes copied before the failure occurred.  The
   coa_bytes_copied value indicates the number of bytes copied but not
   which specific bytes have been copied.

   If the client supports any of the following operations:

   COPY:  for both intra-server and inter-server asynchronous copies

   WRITE_SAME:  for ADB initialization

   then the client is REQUIRED to support the CB_OFFLOAD operation.

   There is a potential race between the reply to the original
   transaction on the forechannel and the CB_OFFLOAD callback on the
   backchannel.  Section of [RFC5661] describes how to handle
   this type of issue.

   Upon success, the coa_resok4.wr_count presents for each operation:

   COPY:  the total number of bytes copied

   WRITE_SAME:  the same information that a synchronous WRITE_SAME would

17.  Security Considerations

   NFSv4.2 has all of the security concerns present in NFSv4.1 (see
   Section 21 of [RFC5661]), as well as those present in the server-side
   copy (see Section 4.9) and in Labeled NFS (see Section 9.6).

18.  IANA Considerations

   The IANA considerations for Labeled NFS are addressed in [RFC7569].

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19.  References

19.1.  Normative References

              The Open Group, "Section 'posix_fadvise()' of System
              Interfaces of The Open Group Base Specifications Issue 7",
              IEEE Std 1003.1, 2016 Edition (HTML Version),
              ISBN 1937218812, September 2016,

              The Open Group, "Section 'posix_fallocate()' of System
              Interfaces of The Open Group Base Specifications Issue 7",
              IEEE Std 1003.1, 2016 Edition (HTML Version),
              ISBN 1937218812, September 2016,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC5661]  Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
              "Network File System (NFS) Version 4 Minor Version 1
              Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,

   [RFC5662]  Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
              "Network File System (NFS) Version 4 Minor Version 1
              External Data Representation Standard (XDR) Description",
              RFC 5662, DOI 10.17487/RFC5662, January 2010,

   [RFC7569]  Quigley, D., Lu, J., and T. Haynes, "Registry
              Specification for Mandatory Access Control (MAC) Security
              Label Formats", RFC 7569, DOI 10.17487/RFC7569, July 2015,

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   [RFC7861]  Adamson, A. and N. Williams, "Remote Procedure Call (RPC)
              Security Version 3", RFC 7861, DOI 10.17487/RFC7861,
              November 2016, <>.

   [RFC7863]  Haynes, T., "Network File System (NFS) Version 4 Minor
              Version 2 External Data Representation Standard (XDR)
              Description", RFC 7863, DOI 10.17487/RFC7863,
              November 2016, <>.

19.2.  Informative References

              Ashdown, L., "Chapter 15: Validating Database Files and
              Backups", Oracle Database Backup and Recovery User's
              Guide 11g Release 1 (11.1), August 2008,

   [Baira08]  Bairavasundaram, L., Goodson, G., Schroeder, B.,
              Arpaci-Dusseau, A., and R. Arpaci-Dusseau, "An Analysis of
              Data Corruption in the Storage Stack", Proceedings of the
              6th USENIX Symposium on File and Storage Technologies
              (FAST '08), 2008,

   [IESG08]   IESG, "IESG Processing of RFC Errata for the IETF Stream",
              July 2008, <

   [LB96]     LaPadula, L. and D. Bell, "MITRE Technical Report 2547,
              Volume II", Journal of Computer Security, Volume 4,
              Issue 2-3, 239-263, IOS Press, Amsterdam, The Netherlands,
              January 1996.

              McDougall, R. and J. Mauro, "Section 11.4.3: Detecting
              Memory Corruption", Solaris Internals: Solaris 10 and
              OpenSolaris Kernel Architecture, 2nd Edition, 2007.

              Noveck, D., "Rules for NFSv4 Extensions and Minor
              Versions", Work in Progress,
              draft-ietf-nfsv4-versioning-07, October 2016.

   [RFC959]   Postel, J. and J. Reynolds, "File Transfer Protocol",
              STD 9, RFC 959, DOI 10.17487/RFC0959, October 1985,

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   [RFC1108]  Kent, S., "U.S. Department of Defense Security Options for
              the Internet Protocol", RFC 1108, DOI 10.17487/RFC1108,
              November 1991, <>.

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, DOI 10.17487/RFC2401,
              November 1998, <>.

   [RFC4506]  Eisler, M., Ed., "XDR: External Data Representation
              Standard", STD 67, RFC 4506, DOI 10.17487/RFC4506,
              May 2006, <>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,

   [RFC5663]  Black, D., Fridella, S., and J. Glasgow, "Parallel NFS
              (pNFS) Block/Volume Layout", RFC 5663,
              DOI 10.17487/RFC5663, January 2010,

   [RFC7204]  Haynes, T., "Requirements for Labeled NFS", RFC 7204,
              DOI 10.17487/RFC7204, April 2014,

   [RFC7230]  Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
              Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7530]  Haynes, T., Ed., and D. Noveck, Ed., "Network File System
              (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
              March 2015, <>.

   [Strohm11] Strohm, R., "Chapter 2: Data Blocks, Extents, and
              Segments", Oracle Database Concepts 11g Release 1 (11.1),
              January 2011,

   [T10-SBC2] Elliott, R., Ed., "ANSI INCITS 405-2005, Information
              Technology - SCSI Block Commands - 2 (SBC-2)",
              November 2004,

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   Tom Haynes would like to thank NetApp, Inc. for its funding of his
   time on this project.

   For the topic "sharing change attribute implementation
   characteristics with NFSv4 clients", the original document was by
   Trond Myklebust.

   For the NFS server-side copy, the original document was by James
   Lentini, Mike Eisler, Deepak Kenchammana, Anshul Madan, and Rahul
   Iyer.  Tom Talpey co-authored an unpublished version of that
   document.  It was also reviewed by a number of individuals: Pranoop
   Erasani, Tom Haynes, Arthur Lent, Trond Myklebust, Dave Noveck,
   Theresa Lingutla-Raj, Manjunath Shankararao, Satyam Vaghani, and Nico
   Williams.  Anna Schumaker's early prototyping experience helped us
   avoid some traps.  Also, both Olga Kornievskaia and Andy Adamson
   brought implementation experience to the use of copy stateids in the
   inter-server copy.  Jorge Mora was able to optimize the handling of
   errors for the result of COPY.

   For the NFS space reservation operations, the original document was
   by Mike Eisler, James Lentini, Manjunath Shankararao, and Rahul Iyer.

   For the sparse file support, the original document was by Dean
   Hildebrand and Marc Eshel.  Valuable input and advice was received
   from Sorin Faibish, Bruce Fields, Benny Halevy, Trond Myklebust, and
   Richard Scheffenegger.

   For the application I/O hints, the original document was by Dean
   Hildebrand, Mike Eisler, Trond Myklebust, and Sam Falkner.  Some
   early reviewers included Benny Halevy and Pranoop Erasani.

   For Labeled NFS, the original document was by David Quigley, James
   Morris, Jarrett Lu, and Tom Haynes.  Peter Staubach, Trond Myklebust,
   Stephen Smalley, Sorin Faibish, Nico Williams, and David Black also
   contributed in the final push to get this accepted.

   Christoph Hellwig was very helpful in getting the WRITE_SAME
   semantics to model more of what T10 was doing for WRITE SAME (10)
   [T10-SBC2].  And he led the push to get space reservations to more
   closely model the posix_fallocate() operation.

   Andy Adamson picked up the RPCSEC_GSSv3 work, which enabled both
   Labeled NFS and server-side copy to provide more secure options.

   Christoph Hellwig provided the update to GETDEVICELIST.

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   Jorge Mora provided a very detailed review and caught some important
   issues with the tables.

   During the review process, Talia Reyes-Ortiz helped the sessions run
   smoothly.  While many people contributed here and there, the core
   reviewers were Andy Adamson, Pranoop Erasani, Bruce Fields, Chuck
   Lever, Trond Myklebust, David Noveck, Peter Staubach, and Mike

   Elwyn Davies was the General Area Reviewer for this document, and his
   insights as to the relationship of this document and both [RFC5661]
   and [RFC7530] were very much appreciated!

Author's Address

   Thomas Haynes
   Primary Data, Inc.
   4300 El Camino Real Ste 100
   Los Altos, CA  94022
   United States of America

   Phone: +1 408 215 1519