Enforcing uniform file-locking for diverse file-locking protocols

• US 20030065796A1
• Filed: 08/28/2002
• Published: 04/03/2003
• Est. Priority Date: 12/05/1997
• Status: Active Grant

• Current Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Borr, Andrea
• Granted Patent: US 7,293,097 B2
• Time in Patent Office: Days
• US Class Current: 709/229
• 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 707/99931 Database or file accessing

Abstract

The invention provides a method and system for correct interoperation of multiple diverse file server or file locking protocols, using a uniform multi-protocol lock management system. A file server determines, before allowing any client device to access data or to obtain a lock, whether that would be inconsistent with existing locks, regardless of originating client device or originating protocol for those existing locks. A first protocol enforces mandatory file-open and file-locking together with an opportunistic file-locking technique, while a second protocol lacks file-open semantics and provides only for advisory byte-range and file locking. Enforcing file-locking protects file data against corruption by NFS client devices. A CIFS client device, upon opening a file, can obtain an “oplock” (an opportunistic lock). When a client device issues a non-CIFS protocol request for the oplocked file, the file server sends an oplock-break message to the CIFS client device, giving the CIFS client device the opportunity to flush any cached write operations and possibly close the file. Allowing NFS and NLM requests to break oplocks ensures that file data remains available to NFS client devices simultaneously with protecting integrity of that file data. A CIFS client device can obtain a “change-monitoring” lock for a directory in the file system, so as to be notified by the file server whenever there is a change to that directory. The file server notes changes to the directory by both CIFS and non-CIFS client devices, and notifies those CIFS client devices with “change-monitoring” locks of those changes.

Claims

1. A method of operating a file server, said method including steps for enforcing a uniform file-locking semantics among a set of client devices using a plurality of diverse file server or file locking protocols.

2. A method as in claim 1, wherein said uniform file-locking semantics includes opportunistic locks capable of

being requested by a first client device using a first protocol;

and

breaking of said opportunistic locks being triggered by a second client device using a second protocol different from said first protocol.

3. A method as in claim 2, wherein said first protocol includes CIFS.

4. A method as in claim 2, wherein said second protocol includes NFS or NLM.

5. A method as in claim 1, wherein said uniform file-locking semantics includes steps for

granting an opportunistic lock on a selected file to a first said client device in response to a first message using a first said protocol;

and

breaking said opportunistic lock in response to a second message using a second said protocol.

6. A method as in claim 5, wherein said steps for breaking include steps for

sending an oplock-break message to said first client device in response to said second message;

delaying execution of a file system request indicated by said second message;

receiving a response to said oplock-break message from said first client device; and

processing and responding to said second message after said step of receiving.

7. A method as in claim 1, wherein said uniform file-locking semantics includes a change-monitoring lock type capable of

being requested by a first client device using a first protocol;

and

a change notification being triggered by a second client device using a second protocol different from said first protocol.

8. A method as in claim 7, wherein said first protocol includes CIFS.

9. A method as in claim 7, wherein said second protocol includes NFS.

10. A method as in claim 1, wherein said uniform file-locking semantics includes steps for

granting a change-monitoring lock on a selected directory to a first said client device in response to a first message using a first said protocol;

and

sending a change-notify message to said first client device in response to a second message regarding said selected directory using a second said protocol.

11. A method as in claim 1, wherein said steps for enforcing include steps for

recognizing a plurality of diverse protocols;

providing a uniform file-locking semantics in response to messages using at least one of said protocols; and

enforcing said uniform file-locking semantics for all said client devices.

12. A method as in claim 11, wherein said uniform file-locking semantics includes steps for

granting an opportunistic lock to a first said client device in response to a first message using a first said protocol;

and

breaking said opportunistic lock in response to a second message using a second said protocol.

13. A method as in claim 12, wherein said steps for breaking include steps for

sending an oplock-break message to said first client device in response to said second message;

delaying execution of a file system request indicated by said second message;

receiving a response to said oplock-break message from said first client device; and

processing and responding to said second message after said step of receiving.

14. A method as in claim 11, wherein said steps for enforcing said uniform file-locking semantics include steps for

granting a change-monitoring lock in response to a first message from a first client device using a first said protocol;

and

sending a change-notify message to said first client device in response to a second message using a second said protocol.

15. A method as in claim 11, wherein said steps for enforcing said uniform file-locking semantics include steps for

recognizing a selected message that attempts to violate said uniform file-locking semantics;

and

responding to said selected message with an error response suited to a protocol associated with said selected message.

16. A method as in claim 11, wherein said steps for enforcing said uniform file-locking semantics include steps for

recognizing a selected message for obtaining a byte-range lock on a file in a selected said protocol, said byte-range lock having a lock type;

and

testing whether obtaining said byte-range lock would conflict with existing locks created by messages using the same or other protocols.

17. A method as in claim 11, wherein said steps for enforcing said uniform file-locking semantics include steps for

recognizing a selected message for opening a file in a selected said protocol, said selected message including a requested access-mode;

and

testing whether opening said file using said requested access-mode would conflict with existing locks created by messages using the same or other protocols.

18. A method as in claim 17,

wherein said selected message includes a requested deny-mode;

and

including steps for testing whether opening said file using said requested deny-mode would conflict with existing locks created by messages using the same or other protocols.

19. A method as in claim 11, wherein said steps for enforcing said uniform file-locking semantics include steps for

recognizing a selected message for reading from or writing to a file in a selected said protocol;

and

testing whether reading from or writing to would conflict with existing locks created by messages using the same or other protocols.

20. A method as in claim 1, wherein said steps for enforcing include steps for

receiving a first message using a first protocol, said first message being operative to lock at least a portion of a selected file;

receiving a second message using a second protocol, said second message being operative to request access to said portion;

comparing said access requested by said second message with said lock, and denying said access if prohibited by said lock.

21. A method as in claim 20, wherein said first protocol includes CIFS.

22. A method as in claim 20, wherein said first protocol or said second protocol includes NLM.

23. A method as in claim 20, wherein said second protocol includes NFS.

24. A method as in claim 20, wherein

said steps for receiving said second message include steps for recognizing said second message as being for obtaining a byte-range lock on a file using said second protocol, said byte-range lock having a lock type;

and

said steps for comparing include steps for testing whether obtaining said byte-range lock having said lock type would conflict with existing locks created by messages using the same or other protocols.

25. A method as in claim 24, wherein said steps for testing are responsive to a protocol used for said second message.

26. A method as in claim 24, wherein said steps for testing operate at file-open time for a first said protocol and at an access time for a second said protocol.

27. A method as in claim 24, wherein said steps for testing operate at file-open time for a first said protocol and at a lock-request time for a second said protocol.

28. A method as in claim 20, wherein

said steps for receiving said second message include steps for recognizing said second message for opening a file using said second protocol, said second message including a requested access-mode;

and

said steps for comparing include steps for testing whether accessing said file using said requested access-mode would conflict with existing locks created by messages using the same or other protocols.

29. A method as in claim 20, wherein

said steps for receiving said second message include steps for recognizing said second message for reading from or writing to a file using said second protocol;

and

said steps for comparing include steps for testing whether accessing said file as attempted by said second message would conflict with existing locks created by messages using the same or other protocols.

30. A method as in claim 20, wherein

said steps for receiving said first message include steps for granting an opportunistic lock in response to said first message;

and

said steps for comparing include steps for breaking said opportunistic lock in response to said second message.

31. A method as in claim 30, wherein said steps for breaking include steps for

sending an oplock-break message to said first client device in response to said second message;

delaying execution of a file system request indicated by said second message;

receiving a response to said oplock-break message from said first client device; and

processing and responding to said second message after said step of receiving.

32. A method as in claim 31, wherein said response to said oplock-break message includes an oplock-break acknowledgement message or a file close message.

33. A method as in claim 1, wherein said file-locking semantics includes a lock mode determined in response to an access-mode and a deny-mode requested by a first client device using a first protocol.

34. A method as in claim 1, wherein said file-locking semantics includes

a first lock mode determined in response to an access-mode and a deny-mode requested by a first client device using a first protocol;

and

a second lock mode determined in response to a message from a second client device using a second protocol different from said first protocol;

wherein said file server is responsive to comparison of said first lock mode with said second lock mode.

35. A method as in claim 34, wherein said comparison includes a lock compatibility matrix.

36. A method as in claim 34, wherein said comparison includes a lock conversion matrix.

37. A method as in claim 34, wherein said second lock mode is responsive to a request for a byte-range lock.

38. A method as in claim 34, wherein said second lock mode is responsive to a request for a NLM file lock.