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Commit 285a0f00 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd: revise 4.1 status documentation 



Some small updates, a caveat about the minorversion control interface,
and an attempt to put missing features in context.

Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent cd68c374

Documentation/filesystems/nfs41-server.txt

+54 −0
Original line number Original line Diff line number Diff line
@@ -11,6 +11,11 @@ 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

control file, the nfsd service must be taken down.  Use your user-mode

nfs-utils to set this up; see rpc.nfsd(8)

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

The NFSv4 minorversion 1 (NFSv4.1) implementation in nfsd is based

on the latest NFSv4.1 Internet Draft:

on the latest NFSv4.1 Internet Draft:

http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-29

http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-29
@@ -25,6 +30,49 @@ are still under development out of tree. 
See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design

See http://wiki.linux-nfs.org/wiki/index.php/PNFS_prototype_design

for more information.

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).

	- no trunking support: no clients currently take advantage of

	  trunking, but this is a mandatory failure, and its use is

	  recommended to clients in a number of places.  (E.g. to ensure

	  timely renewal in case an existing connection's retry timeouts

	  have gotten too long; see section 8.3 of the draft.)

	  Therefore, lack of this feature may cause future clients to

	  fail.

	- 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.

	- Server reboot recovery is unsupported; if the server reboots,

	  clients 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, FREE_STATEID, SECINFO_NO_NAME, and

	  TEST_STATEID, 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, 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 table below, taken from the NFSv4.1 document, lists

the operations that are mandatory to implement (REQ), optional

the operations that are mandatory to implement (REQ), optional

(OPT), and NFSv4.0 operations that are required not to implement (MNI)

(OPT), and NFSv4.0 operations that are required not to implement (MNI)
@@ -142,6 +190,12 @@ NS*| CB_WANTS_CANCELLED | OPT | FDELG, | Section 20.10 | 




Implementation notes:

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:

EXCHANGE_ID:

* only SP4_NONE state protection supported

* only SP4_NONE state protection supported

* implementation ids are ignored

* implementation ids are ignored