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RFC 5661, "Network File System (NFS) Version 4 Minor Version 1 Protocol", January 2010

Note: This RFC has been obsoleted by RFC 8881

Source of RFC: nfsv4 (tsv)

Errata ID: 5212
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT

Reported By: NFS4ERR_ROFS is not a valid error code for LAYOUTGET
Date Reported: 2017-12-19
Held for Document Update by: Magnus Westerlund
Date Held: 2020-09-04

Section 15.2 says:

   | LAYOUTGET            | NFS4ERR_ACCESS, NFS4ERR_ADMIN_REVOKED,     |
   |                      | NFS4ERR_BADIOMODE, NFS4ERR_BADLAYOUT,      |
   |                      | NFS4ERR_BADXDR, NFS4ERR_BAD_STATEID,       |
   |                      | NFS4ERR_DEADSESSION, NFS4ERR_DELAY,        |
   |                      | NFS4ERR_DELEG_REVOKED, NFS4ERR_DQUOT,      |
   |                      | NFS4ERR_FHEXPIRED, NFS4ERR_GRACE,          |
   |                      | NFS4ERR_INVAL, NFS4ERR_IO,                 |
   |                      | NFS4ERR_LAYOUTTRYLATER,                    |
   |                      | NFS4ERR_LAYOUTUNAVAILABLE, NFS4ERR_LOCKED, |
   |                      | NFS4ERR_MOVED, NFS4ERR_NOFILEHANDLE,       |
   |                      | NFS4ERR_NOSPC, NFS4ERR_NOTSUPP,            |
   |                      | NFS4ERR_OLD_STATEID, NFS4ERR_OPENMODE,     |
   |                      | NFS4ERR_OP_NOT_IN_SESSION,                 |
   |                      | NFS4ERR_RECALLCONFLICT,                    |
   |                      | NFS4ERR_REP_TOO_BIG,                       |
   |                      | NFS4ERR_REP_TOO_BIG_TO_CACHE,              |
   |                      | NFS4ERR_REQ_TOO_BIG,                       |
   |                      | NFS4ERR_RETRY_UNCACHED_REP,                |
   |                      | NFS4ERR_SERVERFAULT, NFS4ERR_STALE,        |
   |                      | NFS4ERR_TOOSMALL, NFS4ERR_TOO_MANY_OPS,    |
   |                      | NFS4ERR_UNKNOWN_LAYOUTTYPE,                |
   |                      | NFS4ERR_WRONG_TYPE                         |

It should say:

   | LAYOUTGET            | NFS4ERR_ACCESS, NFS4ERR_ADMIN_REVOKED,     |
   |                      | NFS4ERR_BADIOMODE, NFS4ERR_BADLAYOUT,      |
   |                      | NFS4ERR_BADXDR, NFS4ERR_BAD_STATEID,       |
   |                      | NFS4ERR_DEADSESSION, NFS4ERR_DELAY,        |
   |                      | NFS4ERR_DELEG_REVOKED, NFS4ERR_DQUOT,      |
   |                      | NFS4ERR_FHEXPIRED, NFS4ERR_GRACE,          |
   |                      | NFS4ERR_INVAL, NFS4ERR_IO,                 |
   |                      | NFS4ERR_LAYOUTTRYLATER,                    |
   |                      | NFS4ERR_LAYOUTUNAVAILABLE, NFS4ERR_LOCKED, |
   |                      | NFS4ERR_MOVED, NFS4ERR_NOFILEHANDLE,       |
   |                      | NFS4ERR_NOSPC, NFS4ERR_NOTSUPP,            |
   |                      | NFS4ERR_OLD_STATEID, NFS4ERR_OPENMODE,     |
   |                      | NFS4ERR_OP_NOT_IN_SESSION,                 |
   |                      | NFS4ERR_RECALLCONFLICT,                    |
   |                      | NFS4ERR_REP_TOO_BIG,                       |
   |                      | NFS4ERR_REP_TOO_BIG_TO_CACHE,              |
   |                      | NFS4ERR_REQ_TOO_BIG,                       |
   |                      | NFS4ERR_RETRY_UNCACHED_REP, NFS4ERR_ROFS,  |
   |                      | NFS4ERR_SERVERFAULT, NFS4ERR_STALE,        |
   |                      | NFS4ERR_TOOSMALL, NFS4ERR_TOO_MANY_OPS,    |
   |                      | NFS4ERR_UNKNOWN_LAYOUTTYPE,                |
   |                      | NFS4ERR_WRONG_TYPE                         |

Notes:

It could be argued that the OPEN takes care of a NFS4ERR_ROFS for a LAYOUTGET of a LAYOUTIOMODE4_RW, but that does not explain why WRITE is allowed to return a NFS4ERR_ROFS.

With the Flex File Layout Type, the storage device depends on the metadata server enforcing the read-only filesystem semantics. An NFSv3 WRITE to the storage device might be accepted even though the filesystem might be RO. Further, if a snapshot is taken, the storage device might not be aware of the fact that a data file is in a snapshot.

Currently, if the underlying filesystem determines that the LAYOUTGET for a LAYOUTIOMODE4_RW is going to return NFS4ERR_ROFS, to be spec compliant, it MUST convert the error code to NFS4ERR_SERVERFAULT. The client may then decide to perform IO through the metadata server with NFSv4 WRITE calls, which will in turn get a NFS4ERR_ROFS error. This change pushes the responsibility to be on the LAYOUTGET and allows the client to inform the application of an error earlier.

AD Comments:
This topic requires WG discussion and establishment of consensus. Thus for future document update.

--VERIFIER NOTES--
This topic requires WG discussion and establishment of consensus. Thus for future document update.

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