Methods and apparatus for locking files within a clustered storage environment

• US 5,933,824 A
• Filed: 12/23/1996
• Issued: 08/03/1999
• Est. Priority Date: 12/23/1996
• Status: Expired due to Term

• Current Assignee: NetApp, Inc.
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Fredin, Gerald J., DeKoning, Rodney A.
• Primary Examiner(s): Kulik, Paul V.
• Assistant Examiner(s): ROBINSON, GRETA LEE
• Application Number:
  US08/773,470
• Time in Patent Office: 953 Days
• Field of Search: 707/8, 707/1, 707/10, 707/201, 707/200, 711/100, 395/726
• US Class Current: 1/1
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

Methods and associated apparatus for coordinating file lock requests from a cluster of attached host computer systems within I/O controllers (e.g., intelligent I/O adapters) attached to a storage subsystem. The I/O controllers, operable in accordance with the methods of the present invention, includes semaphore tables used to provide temporary exclusive access to an identified portion of an identified file. The host systems request the temporary exclusive access of a file through the I/O controllers rather than over slower network communication media and protocols as is known in the art. The I/O controllers then manages a plurality of competing lock requests to provide mutual exclusivity of the file access. The file lock management is therefore managed over the higher bandwidth storage interface channels of the host systems and without the generalized network protocols burdening the lock management process and the host system CPUs. The I/O controllers in which the methods of the present invention are operable, as referred to herein, includes the controller within a storage device such as a RAID subsystem and decentralized control storage devices such as a RAID subsystem or a storage subsystem with control decentralized to a plurality of intelligent host adapters associated with the cluster of host systems.

Claims

1. In a clustered computing environment including a plurality of host systems attached to a common storage subsystem, a method operable within I/O controllers associated with said storage subsystem for coordinating exclusive file access within said storage subsystem by said plurality of host systems, said method comprising the steps of:

locking an identified portion of an identified file in response to receipt of a lock request received by one of said I/O controllers from an attached host system wherein the locking step is operable within one of said plurality of I/O controllers; and

releasing the lock of said identified portion of said identified file in response to a release request received by said one of said I/O controllers from said attached host system wherein the releasing step is operable within one of said plurality of I/O controllers.

2. The method of claim 1 further comprising the step of:

deferring processing of requests received from others of said plurality of attached host systems wherein said requests are associated with said identified portion of said identified file wherein the deferring step is operable within one of said plurality of I/O controllers.

3. The method of claim 2 wherein said storage subsystem includes a plurality of controllers for processing of requests received from said plurality of attached host systems and wherein the method further comprises the step of:

designating one of said plurality of controllers as the primary controller with respect to a particular subset of storage within said storage subsystem; and

designating others of said plurality of controllers as secondary controllers with respect to said particular subset of storage.

4. The method of claim 3 wherein the step of locking comprises the steps of:

exchanging file lock request messages between said primary controller and a requesting one of said secondary controllers; and

exchanging file lock grant messages between said primary controller and said requesting one of said secondary controllers.

5. The method of claim 4 wherein the step of releasing the lock comprises the step of:

exchanging file lock release messages between said primary controller and a requesting one of said secondary controllers.

6. The method of claim 2 wherein the step of locking further comprises the steps of:

associating a semaphore with said identified portion of said identified file of said lock request received from said attached host system;

determining that said semaphore is not presently locked in association with another lock request received from an attached host system; and

locking said semaphore in response to the determination that said semaphore is not presently locked.

7. The method of claim 6 wherein the step of deferring processing further comprises the steps of:

adding said lock request to a list of deferred lock requests in response to a determination that said semaphore is presently locked;

determining subsequently that the lock of said semaphore has been released.

8. The method of 7 wherein the step of adding said lock request to a list includes the step of:

informing an attached host system which previously locked said semaphore that said lock request is awaiting release of the lock of said semaphore.

9. In a RAID storage subsystem attached to a plurality of host systems through a plurality of I/O controllers, a method for managing file lock requests received in said plurality of I/O controllers from said plurality of host systems, said method comprising the steps of:

receiving a first lock request in one of said plurality of I/O controllers from one of said plurality of attached host systems, said lock request specifying an identified portion of an identified file for which exclusive access is required;

determining, within one of said plurality of I/O controllers, if a previously received lock request precludes granting exclusive access to said identified portion of said identified file;

granting, within one of said plurality of I/O controllers, the exclusive access of said first lock request in response to the determination that no previously received lock request precludes granting exclusive access to said identified portion of said identified file; and

deferring, within one of said plurality of I/O controllers, the grant of exclusive access of said first lock request in response to the determination that a previously received lock request precludes granting exclusive access to said identified portion of said identified file.

10. The method of claim 9 further comprising the step of:

releasing, within one of said plurality of I/O controllers in response to a release request received in said one of said plurality of I/O controllers from one of said plurality of attached host systems, the exclusive access previously granted in response to a previously received lock request.

11. The method of claim 10 further comprising the step of:

adding, within one of said plurality of I/O controllers, said first lock request to a list of waiting requests in response to the determination that a previously received lock request precludes granting exclusive access to said identified portion of said identified file.

12. The method of claim 11 wherein the releasing step includes the steps of:

locating on said list of waiting request, in response to the releasing step, a next lock request previously received from one of said plurality of attached host systems and deferred in accordance with the deferring step;

removing said next lock request from said list of waiting requests; and

granting the exclusive access requested by said next lock request.

13. The method of claim 10 wherein the step of deferring the grant of exclusive access includes the step of:

pausing processing of said first lock request within said storage subsystem.

14. The method of claim 13 further comprising the steps of:

determining, within one of said plurality of I/O controllers, that no previously received lock request precludes granting exclusive access to said identified portion of said identified file; and

resuming, within one of said plurality of I/O controllers, the processing of said first lock request in response to the determination that no previously received lock request precludes granting exclusive access to said identified portion of said identified file.

15. The method of 9 wherein the step of deferring the grant includes the step of:

informing an attached host system which generated said previously received lock request that said first lock request is awaiting release of said previously received lock request.

16. A method, operable within a plurality of I/O controllers attached to a RAID storage subsystem, for managing file lock requests received in said I/O controllers from a plurality of host systems attached to said RAID storage subsystem wherein one of said plurality of controllers is designated as the primary controller and at least one of said plurality of I/O controllers is designated as the secondary controller, said method comprising the steps of:

receiving, within said secondary controller, a first lock request from one of said plurality of attached host systems, said lock request specifying an identified portion of an identified file for which exclusive access is required;

transmitting a lock request message from said secondary controller to said primary controller to request the granting of said first lock request by said primary controller; and

completing processing of said first lock request in response to receipt of a lock request grant message from said primary controller.

17. The method of claim 16 further comprising the step of

transmitting a lock release message from said secondary controller to said primary controller to relinquish a previously granted file lock request.

18. The method of claim 17 further comprising the step of:

determining, within said primary controller, that a previously granted lock request excludes access to the identified portion of the identified file;

deferring granting of said first lock request in response the determination that a previously granted lock request excludes access to the identified portion of the identified file; and

transmitting a lock request grant message from said primary controller to said secondary controller to grant said first lock request in response to the determination that no previously granted lock request excludes access to the identified portion of the identified file.

19. The method of claim 18 wherein the step within said primary controller of determining that a previously granted lock request excludes access to the identified portion of the identified file includes the step of:

associating a semaphore with said first lock request and determining that no locked semaphore is associated with another lock request which overlaps the identified portion of the identified file of said first lock request.

21. The method of claim 17 wherein the releasing step includes the steps of:

determining, within said primary controller, that processing of other lock request messages has been previously deferred; and

resuming processing, within said primary controller, for at least one of said other lock request messages previously deferred.

22. The method of claim 21 wherein the step of resuming processing includes the step of:

transmitting a lock request grant message from said primary controller to said secondary controller to grant said first lock request in response to the determination that no previously granted lock request excludes access to the identified portion of the identified file.

20. The method of 18 wherein the step of deferring granting includes the step of:

informing an attached host system which generated said previously granted lock request that said first lock request is awaiting release of said previously granted lock request.

23. A method, operable within a system having a plurality of intelligent I/O adapters in a plurality of host systems, for managing file lock requests received from said plurality of host systems wherein one of said plurality of intelligent I/O adapters is designated as the primary controller and at least one of said plurality of intelligent I/O adapters is designated as the secondary controller, said method comprising the steps of:

receiving, within said secondary controller, a first lock request from one of said plurality of attached host systems, said lock request specifying an identified portion of an identified file for which exclusive access is required;

transmitting a lock request message from said secondary controller to said primary controller to request the granting of said first lock request by said primary controller; and

completing processing of said first lock request in response to receipt of a lock request grant message from said primary controller.

24. The method of claim 23 further comprising the step of transmitting a lock release message from said secondary controller to said primary controller to relinquish a previously granted file lock request.

25. The method of claim 24 further comprising the step of:

determining, within said primary controller, that a previously granted lock request excludes access to the identified portion of the identified file;

deferring granting of said first lock request in response the determination that a previously granted lock request excludes access to the identified portion of the identified file; and

transmitting a lock request grant message from said primary controller to said secondary controller to grant said first lock request in response to the determination that no previously granted lock request excludes access to the identified portion of the identified file.

26. The method of claim 25 wherein the step within said primary controller of determining that a previously granted lock request excludes access to the identified portion of the identified file includes the step of:

associating a semaphore with said first lock request and determining that no locked semaphore is associated with another lock request which overlaps the identified portion of the identified file of said first lock request.

27. The method of claim 24 wherein the releasing step includes the steps of:

determining, within said primary controller, that processing of other lock request messages has been previously deferred; and

resuming processing, within said primary controller, for at least one of said other lock request messages previously deferred.

28. The method of claim 27 wherein the step of resuming processing includes the step of:

transmitting a lock request grant message from said primary controller to said secondary controller to grant said first lock request in response to the determination that no previously granted lock request excludes access to the identified portion of the identified file.

29. The method of 25 wherein the step of deferring granting includes the step of:

informing an attached host system which generated said previously granted lock request that said first lock request is awaiting release of said previously granted lock request.

30. A program storage device readable by a computer, tangibly embodying a program or instructions executable by computers in a plurality of I/O controllers connecting a plurality of host computer systems to a common storage subsystem to perform the method steps for coordinating exclusive file access within said storage subsystem by said plurality of host systems, said method steps comprising:

locking an identified portion of an identified file in response to receipt of a lock request received by one of said I/O controllers from an attached host system wherein the locking step is operable within one of said plurality of I/O controllers; and

releasing the lock of said identified portion of said identified file in response to a release request received by said one of said I/O controllers from said attached host system wherein the releasing step is operable within one of said plurality of I/O controllers.

31. The program storage device of claim 30 wherein the method further comprises the step of:

deferring processing of requests received from others of said plurality of attached host systems wherein said requests are associated with said identified portion of said identified file wherein the deferring step is operable within one of said plurality of I/O controllers.

32. The program storage device of claim 31 wherein said storage subsystem includes a plurality of controllers for processing of requests received from said plurality of attached host systems and wherein the method further comprises the step of:

designating one of said plurality of controllers as the primary controller with respect to a particular subset of storage within said storage subsystem; and

designating others of said plurality of controllers as secondary controllers with respect to said particular subset of storage.

33. The program storage device of claim 32 wherein the method step of locking comprises the steps of:

exchanging file lock request messages between said primary controller and a requesting one of said secondary controllers; and

exchanging file lock grant messages between said primary controller and said requesting one of said secondary controllers.

34. The program storage device of claim 33 wherein the method step of releasing the lock comprises the step of:

exchanging file lock release messages between said primary controller and a requesting one of said secondary controllers.

35. The program storage device of claim 31 wherein the method step of locking further comprises the steps of:

associating a semaphore with said identified portion of said identified file of said lock request received from said attached host system;

determining that said semaphore is not presently locked in association with another lock request received from an attached host system; and

locking said semaphore in response to the determination that said semaphore is not presently locked.

36. The program storage device of claim 35 wherein the method step of deferring processing further comprises the steps of:

adding said lock request to a list of deferred lock requests in response to a determination that said semaphore is presently locked;

determining subsequently that the lock of said semaphore has been released.

37. The program storage device of 36 wherein the method step of adding said lock request to a list includes the step of:

informing an attached host system which previously locked said semaphore that said lock request is awaiting release of the lock of said semaphore.