Method, Apparatus and Computer Program Product For Maintaining File System Client Directory Caches With Parallel Directory Writes

In a distributed file system in which a server system stores a server version of a file system directory, a method for synchronizing a client system with the server version of the file system directory, comprising:

• storing a cached client version of the file system directory, the client version reflecting updates to the server version of the file system directory that have been replicated on the client system, wherein the cached client version of the file system directory maintains an updaters count of pending requests from the client system to the server system to update the file system directory;
• incrementing the updaters count upon initiating an update request to the server system;
• decrementing the updaters count upon processing a reply to the update request from the server system;
• wherein the cached client version of the file system directory has a lock associated therewith, the method further comprising:
• acquiring the lock before incrementing the updaters count;
• releasing the lock while awaiting a reply from the server system;
• reacquiring the lock upon receiving the reply from the server system;
• and
• re-releasing the lock upon processing the reply from the server system and decrementing the updaters count.

In a distributed file system in which a server system stores a server version of a file system directory, a method for synchronizing a client system with the server version of the file system directory, comprising:

• storing a cached client version of the file system directory, the client version reflecting updates to the server version of the file system directory that have been replicated on the client system;
• wherein the cached client version of the file system directory stored by the client system maintains a readers count of tasks reading the file system directory, a read waiters flag indicating that one or more tasks are waiting to read the file system directory, and an update waiters flag indicating that one or more tasks are waiting to read the file system directory, the method further comprising:
• upon initiating an update request, determining from the readers count and the read waiters flag whether there are any tasks reading or waiting to read the file system directory;
• if there are no tasks reading or waiting to read the file system directory, continuing with the update request;
• and
• if there are any tasks reading or waiting to read the file system directory, setting the update waiters flag and suspending further processing of the update request.