File Operations with Multiple Level File Locking Techniques

Abstract

File systems which provide several different and improved locking capabilities. An application on a client workstation communicates through a client driver to a server which interfaces with a metadata database, which contains locking information about the files. Applications perform as normal. The client driver provides lock and unlock requests to the server when a write lock or a read with intent to write lock is required. If only a read lock is considered appropriate, the client driver does not provide a lock request. The server transparently performs read operations and read locking using the metadata database without specific requests from the client driver. When a read with intent to write or write lock is required, the lock ownership is placed with a given expiration time. When the time expires the lock is not automatically released but remains with the particular requesting client driver until another client driver requests it.

1 . A file locking system comprising:
 a server providing multi-user access to files;   a client workstation coupled to said server and including a client driver for receiving requests from an application and providing file lock requests to said server; and   a locking mechanism coupled to said server and setting and containing file lock status, the lock status including read, write and read with intent to write states,
 wherein said client driver provides write requests and read with intent to write lock requests to said server but not read lock requests, and 
 wherein said server provides read lock, escalate lock and read with intent to write lock requests to said locking mechanism. 
   
   
   
       2 . The file locking system of  claim 1 ,
 wherein only a single read with intent to write lock may be present for a given file.   
   
   
       3 . The file locking system of  claim 1 ,
 where a write lock is developed by escalation from a read with intent to write lock.   
   
   
       4 . The file locking system of  claim 3 ,
 wherein said locking mechanism delays setting write lock status in response to an escalate lock request from said server until all read locks have been released.   
   
   
       5 . The file locking system of  claim 4 ,
 wherein said server requests a read lock just prior to requesting a read operation of the file and releases the read lock at the first time after said read file operation is committed.   
   
   
       6 . The file locking system of  claim 5 ,
 wherein said server requests said read file operation by opening a file handle, and   wherein said read lock is released after said file handle is opened and prior to said data file actually being read.   
   
   
       7 . The file locking system of  claim 1 ,
 wherein said locking mechanism is a database.