File operations with persistent file locking techniques
View Patent ↗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 method for file locking comprising:
receiving a first file locking request from a first client for a first file;
placing a first file lock with an indication of the first client and an expiration time in response to said first file locking request;
receiving a second file locking request from a second client at a later time than said first file locking request;
in response to said second file locking request, determining if an incompatible, unexpired file lock is present, and if so, rejecting said second file locking request, and if not, placing a second file lock with an indication of the second client and an expiration time; and
in response to said second file locking request, determining if an expired file lock is present, and if so, removing the expired file lock, wherein expired file locks are only removed if a second client requests a file lock.
2. The method of claim 1 , further comprising:
receiving a third file locking request from the first client; and
in response to said third file locking request, extending the expiration time of said first file lock if said first file lock is present and rejecting said third file locking request if said first file lock is not present.
3. A computer readable medium or media having computer executable instructions for performing a method comprising:
receiving a first file locking request from a first client for a first file;
placing a first file lock with an indication of the first client and an expiration time in response to said first file locking request;
receiving a second file locking request from a second client at a later time than said first file locking request;
in response to said second file locking request, determining if an incompatible, unexpired file lock is present, and if so, rejecting said second file locking request, and if not, placing a second file lock with an indication of the second client and an expiration time; and
in response to said second file locking request, determining if an expired file lock is present, and if so, removing the expired file lock, wherein expired file locks are only removed if a second client requests a file lock.
4. The medium or media of claim 3 , the method further comprising:
receiving a third file locking request from the first client; and
in response to said third file locking request, extending the expiration time of said first file lock if said first file lock is present and rejecting said third file locking request if said first file lock is not present.
5. A file locking system comprising:
first and second clients providing first and second file locking requests; and
a file locking mechanism coupled to said first and second clients and setting and containing file lock status,
wherein when said file locking mechanism receives a first file locking request from said first client, said file locking mechanism places a first file lock with an indication of said first client and an expiration time,
wherein when said file locking mechanism receives a second file locking request from said second client, said file locking mechanism determines if an incompatible, unexpired file lock is present, and if so, rejects said second file locking request; and if not, places a second file lock with an indication of said second client and an expiration time,
wherein when said file locking mechanism receives said second file locking request, said file locking mechanism determines if an expired file lock is present, and if so, removes said expired file lock, and
wherein said file locking mechanism only removes expired file locks if said second file lock request is received.
6. The file locking system of claim 5 ,
wherein said first client provides a third file locking request; and
wherein said file locking mechanism extends the expiration time of said first file lock if said first file lock is present when said third file locking request is received and rejects said third file locking request if said first file lock is not present.