3.3.19 Procedure 19: FSINFO - Get static file system Information

SYNOPSIS

      FSINFO3res NFSPROC3_FSINFO(FSINFO3args) = 19;

      const FSF3_LINK        = 0x0001;
      const FSF3_SYMLINK     = 0x0002;
      const FSF3_HOMOGENEOUS = 0x0008;
      const FSF3_CANSETTIME  = 0x0010;

      struct FSINFOargs {
           nfs_fh3   fsroot;
      };

      struct FSINFO3resok {
           post_op_attr obj_attributes;
           uint32       rtmax;
           uint32       rtpref;
           uint32       rtmult;
           uint32       wtmax;
           uint32       wtpref;
           uint32       wtmult;
           uint32       dtpref;
           size3        maxfilesize;
           nfstime3     time_delta;
           uint32       properties;
      };

      struct FSINFO3resfail {
           post_op_attr obj_attributes;
      };

      union FSINFO3res switch (nfsstat3 status) {
      case NFS3_OK:
           FSINFO3resok   resok;
      default:
           FSINFO3resfail resfail;
      };

DESCRIPTION

Procedure FSINFO retrieves nonvolatile file system state information and general information about the NFS version 3 protocol server implementation. On entry, the arguments in FSINFO3args are:

fsroot

A file handle identifying a file object. Normal usage is to provide a file handle for a mount point for a file system, as originally obtained from the MOUNT service on the server.

On successful return, FSINFO3res.status is NFS3_OK and FSINFO3res.resok contains:

obj_attributes

The attributes of the file system object specified in fsroot.

rtmax

The maximum size in bytes of a READ request supported by the server. Any READ with a number greater than rtmax will result in a short read of rtmax bytes or less.

rtpref

The preferred size of a READ request. This should be the same as rtmax unless there is a clear benefit in performance or efficiency.

rtmult

The suggested multiple for the size of a READ request.

wtmax

The maximum size of a WRITE request supported by the server. In general, the client is limited by wtmax since there is no guarantee that a server can handle a larger write. Any WRITE with a count greater than wtmax will result in a short write of at most wtmax bytes.

wtpref

The preferred size of a WRITE request. This should be the same as wtmax unless there is a clear benefit in performance or efficiency.

wtmult

The suggested multiple for the size of a WRITE request.

dtpref

The preferred size of a READDIR request.

maxfilesize

The maximum size of a file on the file system.

time_delta

The server time granularity. When setting a file time using SETATTR, the server guarantees only to preserve times to this accuracy. If this is {0, 1}, the server can support nanosecond times, {0, 1000000} denotes millisecond precision, and {1, 0} indicates that times are accurate only to the nearest second.

properties

A bit mask of file system properties. The following values are defined:

FSF_LINK

If this bit is 1 (TRUE), the file system supports hard links.

FSF_SYMLINK

If this bit is 1 (TRUE), the file system supports symbolic links.

FSF_HOMOGENEOUS

If this bit is 1 (TRUE), the information returned by PATHCONF is identical for every file and directory in the file system. If it is 0 (FALSE), the client should retrieve PATHCONF information for each file and directory as required.

FSF_CANSETTIME

If this bit is 1 (TRUE), the server will set the times for a file via SETATTR if requested (to the accuracy indicated by time_delta). If it is 0 (FALSE), the server cannot set times as requested.

Otherwise, FSINFO3res.status contains the error on failure and FSINFO3res.resfail contains the following:

attributes

The attributes of the file system object specified in fsroot.

IMPLEMENTATION

Not all implementations can support the entire list of attributes. It is expected that a server will make a best effort at supporting all the attributes.

The file handle provided is expected to be the file handle of the file system root, as returned to the MOUNT operation. Since mounts may occur anywhere within an exported tree, the server should expect FSINFO requests specifying file handles within the exported file system. A server may export different types of file systems with different attributes returned to the FSINFO call. The client should retrieve FSINFO information for each mount completed. Though a server may return different FSINFO information for different files within a file system, there is no requirement that a client obtain FSINFO information for other than the file handle returned at mount.

The maxfilesize field determines whether a server's particular file system uses 32 bit sizes and offsets or 64 bit file sizes and offsets. This may affect a client's processing.

The preferred sizes for requests are nominally tied to an exported file system mounted by a client. A surmountable issue arises in that the transfer size for an NFS version 3 protocol request is not only dependent on characteristics of the file system but also on characteristics of the network interface, particularly the maximum transfer unit (MTU). A server implementation can advertise different transfer sizes (for the fields, rtmax, rtpref, wtmax, wtpref, and dtpref) depending on the interface on which the FSINFO request is received. This is an implementation issue.

ERRORS

NFS3ERR_STALE NFS3ERR_BADHANDLE NFS3ERR_SERVERFAULT

SEE ALSO READLINK, WRITE, READDIR, FSSTAT and PATHCONF.