System and method for delegating file system operations

• US 20040243644A1
• Filed: 05/30/2003
• Published: 12/02/2004
• Est. Priority Date: 05/30/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Lin, Yun, Kumar, Rohan, Steere, David Cappers, Pardikar, Shishir Purushottam, Almeida, Danilo DʼAmico
• Granted Patent: US 7,660,829 B2
• Time in Patent Office: Days
• US Class Current: 707/200
• CPC Class Codes: G06F 16/10 File systems; File servers

Abstract

The invention provides a distributed file system configured to delegate file system operations to clients. The client obtains a delegation associated with an object managed by the server. The delegation enables the client to perform a file system operation on behalf of the server. The client caches the object and enables users associated with the client to access the object in accordance with the delegation.

Claims

8. A computer-implemented method for a client to handle a request associated with an object that is managed by a server, the computer-implemented method comprising:

processing the request using a delegation associated with the object, the delegation enabling the client to perform a file system operation on the object on behalf of the server; and

performing a file system operation associated with the request in accordance with the delegation.

9. The computer-implemented method of claim 8, further comprises:

acquiring the delegation from the server; and

recording the delegation for performing further file system operations on the object.

10. The computer-implemented method of claim 8, further comprises:

upgrading the delegation by communicating with the server; and

modifying delegation records to include the upgraded delegation.

11. The computer-implemented method of claim 10, wherein upgrading the delegation includes obtaining a delegation state with sufficient level to perform the file system operation.

12. The computer-implemented method of claim 8, further comprising:

receiving a recall command from the server for recalling the delegation;

performing file system operations in response to the recall command; and

acknowledging the command.

13. The computer-implemented method of claim 12, wherein the recall command includes a downgraded delegation.

14. The computer-implemented method of claim 13, wherein performing file system operations in response to the recall command includes denying the recall command.

15. The computer-implemented method of claim 13, wherein performing file system operations in response to the recall command includes flowing file system states to the server.

16. The computer-implemented method of claim 13, wherein performing file system operations in response to the recall command includes updating data associated with the object on the server.

17. The computer-implemented method of claim 16, wherein updating the data includes writing modified data associated with the object to the server.

18. The computer-implemented method of claim 16, wherein updating the data includes flushing modified data associated with the object to a client-side cache.

19. A computer-implemented method for a client to handle an object that is managed by a server, the computer-implemented method comprising:

receiving a request to access the object;

acquiring a delegation associated with the object, the delegation enabling the client to perform a file system operation on the object on behalf of the server; and

performing the file system operation on the object without additional communications with the server.

20. The computer-implemented method of claim 19, further comprising:

maintaining information about the delegation;

receiving another request to access the object;

in response to the other request, performing another file system operation on the object using the information without additional communications with the server.

21. The computer-implemented method of claim 19, further comprising:

receiving another request to access the object;

upgrading the delegation by communicating with the file server;

obtaining from the server an upgraded delegation having a state with sufficient level to process the other request; and

performing another file system operation based on the upgraded delegation, in response to the other request.

22. The computer-implemented method of claim 19, further comprising:

receiving a recall command from the file server, the recall command including a new delegation having a state with a lower access level;

flowing a file system state that is not covered by the new delegation; and

sending an acknowledgement to the file server.

23. The computer-implemented method of claim 19, further comprising:

receiving a recall command from the file server due to a request by another client to access the shared object, the recall command including a new delegation having a state with a lower access level;

determining whether there is an existing process on the client that would cause the request from the other client to be denied; and

if so, denying the recall command.

24. The computer-implemented method of claim 23, wherein determining whether there is an existing process that would cause the request from the other client to be denied includes determining whether there is an exclusive open associated with the object.

25. The computer-implemented method of claim 22, further comprising writing modified data associated with the shared object to the file server in response to the new delegation.

26. A computer-implemented method for a server to share an object managed by the server with clients, the computer-implemented method comprising:

receiving a first request for accessing the object from a first client; and

issuing a first delegation to the first client, the first delegation enabling the client to perform file system operations on the object.

27. The computer-implemented method of claim 26, wherein the first delegation includes states.

28. The computer-implemented method of claim 27, wherein the states of the first delegation have adequate levels to enable the first client to perform file system operations on the object without further communication with the server.

29. The computer-implemented method of claim 26, further comprising:

receiving a second request for accessing the object from a second client; and

if the second request does not conflict with the first delegation, enabling the second client to access the object.

30. The computer-implemented method of claim 29, wherein enabling the second client to access the object includes issuing a second delegation to the second client and wherein the second delegation conflicts with the first delegation.

31. The computer-implemented method of claim 30, wherein if the second request conflicts with the first delegation, recalling the first delegation from the first client.

32. The computer-implemented method of claim 31, wherein the second request conflicts with the first delegation if the states of the first delegation prevents the server from satisfying the second request.

33. The computer-implemented method of claim 32, wherein recalling the first delegation includes replacing the first delegation with another delegation that does not prevent the server from satisfying the second request.

34. The computer-implemented method of claim 33, wherein recalling the first delegation includes flowing a file system operation that conflicts with the other delegation from the first client to the server.

35. The computer-implemented method of claim 34, wherein recalling the first delegation includes writing back modified data associated with the object from the client to the server.

36. The computer-implemented method of claim 35, wherein recalling the first delegation includes writing back attributes associated with the object from the client to the server.

37. A method for communicating between clients and servers in a distributed file system, comprising:

issuing, by a first client to a server, a first request for a first delegation associated with an object managed by the server, the first delegation enabling the first client to perform a file system operation on the object;

receiving, by the server from the first client, the first request for the first delegation and determining states associated with the delegation;

issuing, by the server to the first client, the first delegation having the determined states; and

receiving, by the first client from the server, the first delegation and performing a file system operation on the object in accordance with the first delegation.

38. The method of claim 37, further comprising:

receiving, by the server from a second client, a second request for accessing the object, the request conflicting with the first delegation; and

issuing, by the server to a second client, permission to access the object.

39. The method of claim 38, wherein the request from the second client for accessing the object includes a request for a second delegation and wherein the permission to access the object issued by the server includes the second delegation for the second client.

40. The method of claim 37, further comprising:

receiving, by the server from a second client, a second request for accessing the object, the second request conflicting with the first delegation; and

issuing, by the server to a first client, a recall command for recalling the first delegation.

41. The method of claim 40, wherein the recall command includes a modified first-delegation that is compatible with the second request.

42. The method of claim 40, further comprising:

receiving, by the first client from the server, the recall command and configuring operations associated with the object in accordance with the recall command; and

issuing, by the first client to the server, an acknowledgement.

43. The method of claim 40, further comprising flowing, by the first client to the server, file system operations that conflict with the recall command.

44. The method of claim 40, further comprising:

receiving, by the server from the first client, the acknowledgement command; and

issuing, by the server to the second client, permission to access the object.

45. A computer-implemented method for coordinating between a client and a server in a distributed environment, comprising:

determining, by the client, a plurality of client delegation records;

determining, by the server, a plurality of server delegation records;

determining if the client delegation records and the server delegation records match; and

if the client delegation records and the server delegation records do not match, synchronizing the client delegation records and the server delegation records.

46. The computer-implemented method of claim 45, wherein the client delegation records include a client delegation serial number (DSN), wherein the server delegation records include a server DSN, and wherein determining if the client delegation records and the server delegation records match includes comparing the client DSN and the server DSN.

47. The computer-implemented method of claim 46, wherein the client delegation records include client delegation identification numbers (DINs), wherein the server delegation records include server DINs, and wherein determining if the client delegation records and the server delegation records match includes comparing the client DINs and the server DINs.

48. The computer-implemented method of claim 47, wherein the client delegation records include a client delegation count, wherein the server delegation records include a server delegation count, and wherein determining if the client delegation records and the server delegation records match includes comparing the client delegation count and the server delegation count.

49. The computer-implemented method of claim 47, wherein synchronizing the client delegation records and the server delegation records includes discarding a delegation associated with a client DIN.

50. The computer-implemented method of claim 47, wherein synchronizing the client delegation records and the server delegation records includes discarding a delegation associated with a server DIN.

51. The computer-implemented method of claim 47, wherein synchronizing the client delegation records and the server delegation records includes validating a delegation associated with a server DIN.

52. The computer-implemented method of claim 47, wherein synchronizing the client delegation records with the server delegation records includes updating the client DSN.

53. A distributed file system for sharing an object, comprising:

a first client configured to obtain a delegation associated with the object, the delegation enabling the first client to perform an file system operation; and

a file server configured to manage the object and to issue the delegation associated with the object.

54. The system of claim 53, wherein the first client is configured to perform the file system operation in accordance with the delegation without communicating with the server.

55. The system of claim 53, wherein the first client is configured to cache the object and to enable a user to access the cached object.

56. The system of claim 53, wherein the file server is configured to enable a second client to access the object while the delegation is issued to the first client.

57. The system of claim 56, wherein to enable a second client to access the object, the file server is configured to recall the delegation from the first client.

58. The system of claim 57, wherein to recall the delegation includes to issue a modified delegation to the first client.

59. The system of claim 58, wherein the first client is configured to flow a file system operation that conflicts with the modified delegation to the file server.

60. A computer-readable medium encoded with a data structure, comprising:

a first data field containing delegations associated with shared objects managed by a server;

a second data field containing states, each of the states being associated with a delegation in the first data field; and

a third data filed containing cached objects derived from the shared objects.

61. The computer-readable medium of claim 60, wherein the states in the second data field include an open delegation state.

62. The computer-readable medium of claim 60, wherein the states in the second data field include a data delegation state.

63. The computer-readable medium of claim 60, wherein the states in the second data field include an attribute delegation state.

64-1. The computer-readable medium of claim 64, further comprising:

a fifth data field containing delegation identification numbers (DINs), each of the DINs being associated with a delegation in first data field.

65. A distributed file system for sharing an object, comprising:

means for a first client to obtain a delegation associated with an object managed by a server;

means for the first client to cache the object; and

means for the first client to enable users associated with the client to access the object in accordance with the delegation.

66. The distributed file system of claim 65, further comprising:

means for a server to issue the delegation to the first client; and

means for the server to enable a second client to access the object.

67. The distributed file system of claim 65, further comprising:

means for the server to recall the delegation from the first client; and

means for the client to respond to the server recalling the delegation.

68. The distributed file system of claim 65, further comprising:

means for synchronizing delegation records of the first client and delegation records of the server.

69. The distributed file system of claim 65, further comprising:

means for synchronizing delegation records of the first client and delegation records of the server using round trip optimization.

70. The distributed file system of claim 65, further comprising:

means for synchronizing delegation records of the first client and delegation records of the server using count optimization.

71. A computer-implemented method for handling an object that is managed by a server, the computer-implemented method comprising:

providing, by the server to a first client, a delegation associated with the object, the delegation enabling the first client to perform a file system operation on the object without keeping on the server a file handle associated with the object, the delegation including states, each state granting to the client a right to perform a file system operation; and

maintaining, by the first client, the states associated with the delegation independent of an active communication link with the server.

72. The computer-implemented method of claim 71, further comprising:

receiving a request from a second client to access the object, the request requiring a right granted by a state in the delegation;

recalling the delegation to reacquire the required state from the first client; and

granting the request from the second client to access the object.

73. The computer-implemented method of claim 71, further comprising locally maintaining, by the first client, open states associated the object independent of the states associated with the delegation.