Adding an Uncacheable Directory-Entry Metadata Attribute to NFSv4.2

Network File System version 4.2 (NFSv4.2) clients may cache directory-entry (dirent) metadata returned by READDIR to improve performance. Such caching typically assumes that directory-entry metadata and visibility are identical for all users of a client. In some deployments, however, directory-entry metadata or visibility observed by a client may vary over time or across clients due to server policy or other factors. Reuse of cached directory-entry metadata across users can therefore result in clients presenting directory contents or attributes that do not reflect the current state of the server. This document introduces an uncacheable dirent metadata attribute for NFSv4.2 that allows servers to advise clients that directory-entry metadata returned by READDIR and related operations should not be reused across users.