Method, apparatus and computer program product for maintaining file system client directory caches with parallel directory writes

Abstract

A cached version of a file system directory is synchronized with a server version of the directory in a distributed file system. Both a server and a client specify version numbers for their directory versions. On receiving a request from the client specifying a directory update, the server updates its version, increments its version number, and transmits a reply to the client containing a change log with the incremented version number. Upon receiving the reply, the client compares the received version number with that of its cached version. If the version number matches that of the next expected update, the client applies the updates to its cached version and increments its version number. Otherwise, it adds the received change log to a change log queue for the directory without incrementing the last applied version. Mechanisms are provided for handling parallel read and update requests without awaiting replies from the server.