Servers do not physically mount file systems. NFS-style servers connect to the file hierarchy at the directory that their client has NFS-mounted, and they access only those files that are in these NFS-mounted directories or lower in the hierarchy within the same physically-mounted file system.

DFS-style servers export whole mounted file systems. They connect to the file hierarchy at the root directory of those file systems.

The Resolve Path Name service, v_rpn(), is called to implement an NFS mount. The input is the directory pathname, as sent by the client. The primary output is a VFS token for the file system that the directory belongs to and the file ID (FID) of the directory. These represent a VFS and its root directory. With this information the VFS server can access any file in the same file system at or below that directory in the hierarchy.

The export service, v_export(), is called by file exporters. Its input is a file system name and its output is the same as it is for v_rpn().

If several directories in the same real file system are mounted by NFS clients, the VFS server receives the same VFS token for each v_rpn() that is issued during those NFS mounts. This fact is not significant to the VFS server, which associates each VFS token that is obtained with the NFS mount that was performed; there should not be any concern for the physical mount structure that underlies the file hierarchy.

The path name that is passed to v_rpn() may be a regular file; in fact, determining whether it is a file or a directory may be the sole objective of the operation. Usually, though, the path name refers to a directory that serves as a base from which other files are accessed. This access involves path name resolution, which is explained inResolving the pathname of a file or directory.

When a client NFS unmounts the directory, the VFS server can release whatever information it is maintaining about the mount. This includes releasing any cached vnode tokens. The VFS server does not have to inform z/OS UNIX or release the VFS token in any way.

When a file exporter is finished with a file system it calls v_export() to unexport it.