File manager providing distributed locking and metadata management for shared data access by clients relinquishing locks after time period expiration

• US 6,389,420 B1
• Filed: 09/30/1999
• Issued: 05/14/2002
• Est. Priority Date: 09/30/1999
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Darcy, Jeffrey Jon, Searls, Ronald Curtis, Zuckerman, Boris, Jiang, Xiaoye, Vahalia, Uresh K.
• Primary Examiner(s): Mizrahi, Diane D.
• Assistant Examiner(s): ALAUBAIDI, HAYTHIM J
• Application Number:
  US09/410,514
• Time in Patent Office: 957 Days
• Field of Search: 707/8, 707/9, 707/10, 707/200, 707/201, 707/202, 707/203, 707/204, 707/205, 709/248, 709/232, 709/229, 714/4
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1774 Locking methods, e.g. locking methods for file systems allowing shared and concurrent access to files
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

File locks and file metadata are distributed from a file manager to clients in a data network to permit the clients to share access to file data in data storage. The file manager is permitted to grant a second lock upon the file data without necessarily receiving notification from a client that it has relinquished a first lock on the file data while ensuring that conflicting locks are never granted. The client sets the beginning of a first period of time over which the client may access the file data once the first lock on the file data has been granted by the file manager, and the client sends a lock request to the file manager. The file manager responds by setting the beginning of a second period of time such that the first period of time is certain to have expired once the second period of time has expired, granting the first lock upon the file data to the client, and transmitting a lock grant message to the client. The client receives the lock grant message, and accesses the file data so long as the client'"'"'s access to the file data will be completed by expiration of the first period of time.

Claims

1. In a data storage network in which file locks and file metadata are distributed from at least one file manager to network clients to permit the network clients to share access to file data in data storage, a method for permitting the file manager to grant a second lock upon the file data without necessarily receiving notification from a client that it has relinquished a first lock on the file data while ensuring that conflicting locks are never granted, said method comprising the steps of:

a) a client setting the beginning of a first period of time over which the client may access the file data once the first lock on the file data has been granted by the file manager, and the client sending a lock request to the file manager for obtaining the first lock on the file data;

b) the file manager receiving the lock request from the client, and responding by setting the beginning of a second period of time such that the first period of time is certain to have expired once the second period of time has expired, and granting the first lock upon the file data to the client, and transmitting a lock grant message to the client, and

c) the client receiving the lock grant message, and accessing the file data so long as the client'"'"'s access to the file data will be completed by expiration of the first period of time,

whereby the file manager is free to grant a second lock upon the file data after expiration of the second period of time without conflict between the first lock upon the file data and the second lock upon the file data.

2. The method as claimed in claim 1, wherein the file manager returns metadata of the file to the client along with the lock grant message.

3. The method as claimed in claim 1, wherein the client'"'"'s access to the file data modifies the metadata of the file, and the client returns the modified metadata of the file to the file manager after accessing the file data.

4. The method as claimed in claim 1, wherein the client performs more than one transaction upon the file data during the firs t period of time, and sends new metadata of the file t o t he file manager in a commit operation after performing each transaction.

5. The method as claimed in claim 1, wherein the client sends to the file manager a request for an extension of the first lock upon the file data before expiration of the first period of time.

6. The method as claimed in claim 1, wherein the client sends a message to the file manager confirming that the client has relinquished the first lock upon the file data by the expiration of the first period of time, and the file manager detects a failure to receive the message confirming that the client has relinquished the first lock upon the file data by the expiration of the second period of time, and upon detecting the failure, the file manager logs an error.

7. The method as claimed in claim 6, wherein the file manager begins an error recovery procedure by checking whether the client may have performed an access to the file data that would modify metadata of the file.

8. The method as claimed in claim 7, wherein the file manager finds that the client may have performed an access to the file data that would modify the metadata of the file, and recovers modified metadata of the file.

9. The method as claimed in claim 7, wherein the file manager finds that the client may have performed an access to the file data that would modify the metadata of the file, but the file manager is unable to recover modified metadata of the file, and records that the file is possibly corrupted.

10. The method as claimed in claim 1, wherein the client sets the beginning of the first period of time by setting a timer that is serviced by a periodic interrupt routine.

11. The method as claimed in claim 10, wherein the timer activates an error handler at the expiration of the first period of time when the client has failed to relinquish the lock on the file data.

12. The method as claimed in claim 10, wherein the client performs more than one access of the file data, and after each access of the file data, inspects the timer to determine whether there is sufficient time remaining to perform another access of the file data before expiration of the first period of time.

13. The method as claimed in claim 1, wherein the file manager sets the beginning of the second period of time by setting a timer that is serviced by a periodic interrupt routine.

14. The method as claimed in claim 13, wherein the timer activates an error handler at the expiration of the second period of time when the file manager has failed to receive a message from the client confirming that the client has relinquished the first lock upon the file data.

15. The method as claimed in claim 1, wherein the file manager maintains a log of file locks that are granted to the clients, the log including at least information about locks that have not yet expired.

16. The method as claimed in claim 15, wherein a record is recorded in the log for each lock that has been granted, and the record indicates the client to whom the lock has been granted, the file data which has been locked, a grant time for the lock, an expiration time for the lock, and any time of receipt of confirmation that the lock has been relinquished by the client to whom the lock has been granted.

17. A data storage network comprising data storage and at least one file manager coupled to network clients for distributing file locks and file metadata from the file manager to the network clients to permit the network clients to share access to file data in the data storage, the file manager being permitted to grant a second lock upon the file data without necessarily receiving notification from a client that it has relinquished a first lock on the file data while ensuring that conflicting locks are never granted, wherein a network client and the lock manager are programmed to grant, use, and release the first lock on the file data by:

a) the client setting the beginning of a first period of time over which the client may access the file data once the first lock on the file data has been granted by the file manager, and the client sending a lock request to the file manager for obtaining the first lock on the file data;

b) the file manager receiving the lock request from the client, and responding by setting the beginning of a second period of time such that the first period of time is certain to have expired once the second period of time has expired, and granting the first lock upon the file data to the client, and transmitting a lock grant message to the client, and

c) the client receiving the lock grant message, and accessing the file data so long as the client'"'"'s access to the file data will be completed by expiration of the first period of time,

whereby the file manager is free to grant a second lock upon the file data after expiration of the second period of time without conflict between the first lock upon the file data and the second lock upon the file data.

18. The data storage network as claimed in claim 17, wherein the file manager is programmed to return metadata of the file to the client along with the lock grant message.

19. The data storage network as claimed in claim 17, wherein the client is programmed to modify metadata of the file during access to the file data, and the client is programmed to return the modified metadata of the file to the file manager after accessing the file data.

20. The data storage network as claimed in claim 17, wherein the client is programmed to perform more than one transaction upon the file data during the first period of time, and to send new metadata of the file to the file manager in a commit operation after performing at least one transaction.

21. The data storage network as claimed in claim 17, wherein the client is programmed to send to the file manager a request for an extension of the first lock upon the file data before expiration of the first period of time.

22. The data storage network as claimed in claim 17, wherein the client is programmed to send a message to the file manager confirming that the client has relinquished the first lock upon the file data by the expiration of the first period of time, and the file manager is programmed to detect a failure to receive the message confirming that the client has relinquished the first lock upon the file data by the expiration of the second period of time, and upon detecting the failure, to log an error.

23. The data storage network as claimed in claim 22, wherein the file manager is programmed to begin an error recovery procedure by checking whether the client may have performed an access to the file data that would modify metadata of the file.

24. The data storage network as claimed in claim 23, wherein the file manager is programmed to recover modified metadata of the file upon finding that the client may have performed an access to the file data that would modify the metadata of the file.

25. The data storage network as claimed in claim 22, wherein the file manager is programmed to record that the file is possibly corrupted upon finding that the client may have performed an access to the file data that would modify the metadata of the file but the modified metadata of the file cannot be recovered.

26. The data storage network as claimed in claim 17, wherein the client is programmed to set the beginning of the first period of time by setting a timer that is serviced by a periodic interrupt routine.

27. The data storage network as claimed in claim 26, wherein the timer activates an error handler at the expiration of the first period of time when the client has failed to relinquish the lock on the file data.

28. The data storage network as claimed in claim 26, wherein the client is programmed to perform more than one access of the file data, and after each access of the file data, to inspect the timer to determine whether there is sufficient time remaining to perform another access of the file data before expiration of the first period of time.

29. The data storage network as claimed in claim 17, wherein the file manager is programmed to set the beginning of the second period of time by setting a timer that is serviced by a periodic interrupt routine.

30. The data storage network claimed in claim 29, wherein the timer activates an error handler at the expiration of the second period of time when the file manager has failed to receive a message from-the client confirming that the client has relinquished the first lock upon the file data.

31. The data storage network as claimed in claim 17, wherein the file manager is programmed to maintain a log of file locks that are granted to the clients, the log including at least information about locks that have not yet expired.

32. The data storage network as claimed in claim 31, wherein the file manager is programmed to record a record in the log for each lock that has been granted, and the record indicates the client to whom the lock has been granted, the file data which has been locked, a grant time for the lock, an expiration time for the lock, and any time of receipt of confirmation that the lock has been relinquished by the client to whom the lock has been granted.

33. A file manager for use in a data storage network in which file locks and file metadata are distributed from the file manager to the network clients to permit the network clients to share access to file data in the data storage, the file manager comprising

a processor,

a memory coupled to the processor for execution of a program contained in the memory, and

a network port for coupling the processor to the network clients for the distribution of the file locks and the file metadata to the clients,

wherein the program is executable by the processor for the file manager receiving a lock request from the client, and responding by setting the beginning of a period of time such that the period of time is certain to have expired once the client relinquishes a lock upon the file data, granting the lock upon the file data, and transmitting a lock grant message to the client.

34. The file manager as claimed in claim 33, wherein the program is executable by the processor to return metadata of the file to the client along with the lock grant message.

35. The file manager as claimed in claim 33, wherein the program is executable by the processor to grant a request from the client for an extension of the lock upon the file data received before expiration of the period of time.

36. The file manager as claimed in claim 33, wherein the program is executable by the processor to detect a failure to receive message a message from the client confirming that the client ha s relinquished the lock upon the file data by the expiration of the period of time, and upon detecting the failure, to log an error.

37. The file manager as claimed in claim 36, wherein the program is executable by the processor to begin an error recovery procedure by checking whether the client may have performed an access to the file data that would modify metadata of the file.

38. The file manager as claimed in claim 37, wherein the program is executable by the processor to recover modified metadata of the file upon finding that the client may have performed an access to the file data that would modify the metadata of the file.

39. The file manager as claimed in claim 37, wherein the program is executable by the processor to record that the file is possibly corrupted upon finding that the client may have performed an access to the file data that would modify the metadata of the file but the modified metadata of the file cannot be recovered.

40. The file manager as claimed in claim 33, wherein the program is executable by the processor to set the beginning of the period of time by setting a timer that is serviced by a periodic interrupt routine.

41. The file manager as claimed in claim 40, wherein the timer activates an error handler at the expiration of the period of time when the file manager has failed to receive a message from the client confirming that the client has relinquished the lock upon the file data.

42. The file manager as claimed in claim 33, wherein the program is executable by the processor to maintain a log of file locks that are granted to the clients, the log including at least information about locks that have not yet expired.

43. The file manager as claimed in claim 42, wherein the program is executable by the processor to record a record in the log for each lock that has been granted, and the record indicates the client to whom the lock has been granted, the file data which has been locked, a grant time for the lock, an expiration time for the lock, and any time of receipt of confirmation that the lock has been relinquished by the client to whom the lock has been granted.

44. A client for use in a data storage network including at least one file manager distributing file locks and file metadata from the file manager to network clients to permit the network clients to share access to file data in data storage, wherein the client comprises

a processor,

a memory coupled to the processor for execution of a program contained in the memory, and

a network port for coupling the processor to the file manager for receiving file locks and the file metadata from the file manager,

wherein the program is executable by the processor for the client setting the beginning of a period of time over which the client may access the file data once a lock on the file data has been granted by the file manager, and the client sending a lock request to the file manager for obtaining the lock on the file data;

and

wherein the program is executable by the processor for the client receiving a lock grant message from the file manager, and accessing the file data so long as the client'"'"'s access to the file data will be completed by expiration of the period of time.

45. The client as claimed in claim 44, wherein the program is executable by the processor to modify metadata of the file during access to the file data, and to send modified metadata of the file to the file manager after accessing the file data.

46. The client as claimed in claim 44, wherein the program is executable by the processor to perform more than one transaction upon the file data during the period of time, and to send new metadata of the file to the file manager in a commit operation after performing at least one transaction.

47. The client as claimed in claim 44, wherein the program is executable by the processor to send to the file manager a request for an extension of the lock upon the file data before expiration of the period of time.

48. The client as claimed in claim 44, wherein the program is executable by the processor to send a message to the file manager confirming that the client has relinquished the lock upon the file data by the expiration of the period of time.

49. The client as claimed in claim 44, wherein the program is executable by the processor to set the beginning of the period of time by setting a timer that is serviced by a periodic interrupt routine.

50. The client as claimed in claim 49, wherein the program is executable by the processor so that the timer activates an error handler at the expiration of the first period of time when the client has failed to relinquish the lock on the file data.

51. The client as claimed in claim 44, wherein the program is executable by the processor to perform more than one access of the file data, and after each access of the file data, to inspect the timer to determine whether there is sufficient time remaining to perform another access of the file data before expiration of the period of time.

52. A program storage device containing a program for a file manager in a data storage network in which file locks and file metadata are distributed from the file manager to the network clients to permit the network clients to share access to file data in the data storage, wherein the program is executable by the file manager for the file manager receiving a lock request from the client, and responding by setting the beginning of a period of time such that the period of time is certain to have expired once the client relinquishes a lock upon the file data, and granting the lock upon the file data, and transmitting a lock grant message to the client.

53. The program storage device as claimed in claim 52, wherein the program is executable by the file manager to return metadata of the file to the client along with the lock grant message.

54. The program storage device as claimed in claim 52, wherein the program is executable by the file manager to grant a request from the client for an extension of the first lock upon the file data received before expiration of the period of time.

55. The program storage device as claimed in claim 52, wherein the program is executable by the file manager to detect a failure to receive message a message from the client confirming that the client has relinquished the lock upon the file data by the expiration of the period of time, and upon detecting the failure, to log an error.

56. The program storage device as claimed in claim 55, wherein the program is executable by the file manager to begin an error recovery procedure by checking whether the client may have performed an access to the file data that would modify metadata of the file.

57. The program storage device as claimed in claim 56, wherein the program is executable by the file manager to recover modified metadata of the file upon finding that the client may have performed an access to the file data that would modify the metadata of the file.

58. The program storage device as claimed in claim 56, wherein the program is executable by the file manager to record that the file is possibly corrupted upon finding that the client may have performed an access to the file data that would modify the metadata of the file but the modified metadata of the file cannot be recovered.

59. The program storage device as claimed in claim 52, wherein the program is executable by the file manager to set the beginning of the period of time by setting a timer that is serviced by a periodic interrupt routine.

60. The program storage device as claimed in claim 59, wherein the program is executable by the file manger so that the timer activates an error handler at the expiration of the period of time when the file manager has failed to receive a message from the client confirming that the client has relinquished the first lock upon the file data.

61. The program storage device as claimed in claim 52, wherein the program is executable by the file manager to maintain a log of file locks that are granted to the clients, the log including at least information about locks that have not yet expired.

62. The program storage device as claimed in claim 61, wherein the program is executable by the file manager to record a record in the log for each lock that has been granted, and the record indicates the client to whom the lock has been granted, the file data which has been locked, a grant time for the lock, an expiration time for the lock, and any time of receipt of confirmation that the lock has been relinquished by the client to whom the lock has been granted.

63. A program storage device containing a program for a client for use in a data storage network including at least one file manager distributing file locks and file metadata from the file manager to network clients to permit the network clients to share access to file data in data storage,

wherein the program is executable by the client for setting the beginning of a period of time over which the client may access the file data once a lock on the file data has been granted by the file manager, and the client sending a lock request to the file manager for obtaining the lock on the file data;

and

wherein the program is executable by the client for receiving a lock grant message from the file manager, and accessing the file data so long as the client'"'"'s access to the file data will be completed by expiration of the period of time.

64. The program storage device as claimed in claim 63, wherein the program is executable by the client to modify metadata of the file during access to the file data, and to send modified metadata of the file to the file manager after accessing the file data.

65. The program storage device as claimed in claim 63, wherein the program is executable by the client to perform more than one transaction upon the file data during the period of time, and to send new metadata of the file to the file manager in a commit operation after performing at least one transaction.

66. The program storage device as claimed in claim 63, wherein the program is executable by the client to send to the file manager a request for an extension of the lock upon the file data before expiration of the period of time.

67. The program storage device as claimed in claim 63, wherein the program is executable by the client to send a message to the file manager confirming that the client has relinquished the lock upon the file data by the expiration of the period of time.

68. The program storage device as claimed in claim 63, wherein the program is executable by the client to set the beginning of the period of time by setting a timer that is serviced by a periodic interrupt routine.

69. The program storage device as claimed in claim 68, wherein the program is executable by the client so that the timer activates an error handler at the expiration of the period of time when the client has failed to relinquish the lock on the file data.

70. The program storage device as claimed in claim 63, wherein the program is executable by the client to perform more than one access of the file data, and after each access of the file data, to inspect the timer to determine whether there is sufficient time remaining to perform another access of the file data before expiration of the period of time.