Transactional file system

• US 20050138085A1
• Filed: 12/13/2004
• Published: 06/23/2005
• Est. Priority Date: 03/30/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Miller, Thomas J., Atkinson, Robert G., Verma, Surendra
• Granted Patent: US 7,418,463 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1865 Transactional file systems
• CPC Class Codes: Y10S 707/959 Network
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99937 Sorting
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A transactional file system wherein multiple file system operations may be performed as part of a user-level transaction. An application specifies that the operations on a file, or the file system operations of a thread, should be handled as part of a transaction, and the application is given a file handle associated with a transaction context. For file system requests associated with a transaction context, a component within the file system manages the operations consistent with transactional behavior. The component, which may be a resource manager for distributed transactions, provides data isolation by providing multiple versions of a file by tracking copies of pages that have changed, such that transactional readers do not receive changes to a file made by transactional writers, until the transactional writer commits the transaction and the reader reopens the file. The component also handles namespace logging operations in a multiple-level log that facilitates logging and recovery. Page data is also logged separate from the main log, with a unique signature that enables the log to determine whether a page was fully flushed to disk prior to a system crash. Namespace isolation is provided until a transaction commits via isolation directories, whereby until committed, a transaction sees the effects of its own operations not the operations of other transactions. Transactions over a network are also facilitated via a redirector protocol.

Claims

12. A computer-readable medium having computer-executable instructions, which when executed perform steps, comprising:

opening a file in association with a first transaction; and

maintaining data at a file system level while the first transaction has not committed to isolate changes to the file made in association with the first transaction from being accessed by a second transaction.

1. In a computing environment, a computer-implemented method, comprising:

receiving a first request to open a file, the request associated with a first transaction;

opening a first instance of the file, and maintaining information indicating that the first instance of the file is associated with the first transaction;

receiving a second request to open the file;

opening a second instance of the file;

receiving a change to data of the second instance of the file;

maintaining data to isolate a first version of the file corresponding to the first instance from a second version of the file corresponding to the second instance;

receiving a read request to read the file, the read request associated with the first transaction;

determining that that the first version of the file is associated with a first transaction; and

reading data corresponding to the first version of the file in response to the read request.

2. The method of claim 1 wherein maintaining data to isolate the first version of the file from the second version of the file includes maintaining the change to the data of the second version of the file distinct from data of the first version of the file.

3. The method of claim 2 further comprising, writing a change to the file in response to receiving the change to data, and wherein maintaining the change to the data of the second version of the file distinct from data of the first version of the file includes preserving a copy of a portion of the first version of the file to a first data structure prior to writing the change to the file.

4. The method of claim 3 wherein maintaining data to isolate the first version of the file from the second version of the file includes maintaining a second data structure to map a location of the copy of the portion.

5. The method of claim 4 wherein the portion corresponds to at least one page, and wherein the second data structure records each page number corresponding to a change.

6. The method of claim 4 wherein reading data corresponding to the first version of the file in response to the read request includes accessing the second data structure to determine at least one location of the file data in the first data structure corresponding to the read request.

7. The method of claim 4 further comprising logging information corresponding to the change to the data to a record in a log, and wherein the second data structure further includes information identifying the record.

8. The method of claim 1 wherein the second request is associated with a second transaction.

9. The method of claim 1 wherein the first request to open the file corresponds to a read-only request.

10. The method of claim 1 further comprising, receiving a close request to close the file, the close request associated with the first transaction, closing the file with respect to the first transaction, receiving a third request to open the file, the third request associated with the first transaction, receiving a request to access data in the file from the first transaction, and accessing data in the file corresponding to the second version in response to the request to access data.

11. A computer-readable medium having computer-executable instructions, which when executed perform the method of claim 1.

13. The computer-readable medium of claim 12 further comprising logging information corresponding to the changes made to the file to a log.

14. The computer-readable medium of claim 13 wherein the changes made to the file in association with the first transaction are to actual file locations of the file, and wherein maintaining information from which a read-only version of the file is preserved for the second transaction comprises copying data from the actual file locations before they are overwritten with the changes.

15. The computer-readable medium of claim 13 wherein the changes are made in a cache that is written to the actual file locations.

13-1. The computer-readable medium of claim 12 wherein maintaining the data comprises maintaining information from which a read-only version of the file is preserved for the second transaction.

16. In a computing environment, a method comprising:

opening a past version of a file for read-only access, including opening a current version of the file and accessing a change data structure that contains information for locating file data for the past version when corresponding file data in the current version has changed;

opening the file for read-write access in association with a transaction; and

updating the change data structure when changes are written to the current version of the file so that the past version is preserved for the read-only access.

17. The method of claim 16 wherein updating the change data structure includes writing at least one page number that corresponds to the changed file data.

18. The method of claim 16 wherein updating the change data structure includes writing a log sequence number that corresponds to the changed file data.

19. A computer-readable medium having computer-executable instructions, which when executed perform the method of claim 16.