Transaction-safe FAT file system improvements

• US 7,363,540 B2
• Filed: 06/25/2004
• Issued: 04/22/2008
• Est. Priority Date: 10/22/2002
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Gopalan, Yadhu N., Patel, Sachin
• Primary Examiner(s): CHU, GABRIEL L
• Application Number:
  US10/876,425
• Publication Number:
  US 20040250172A1
• Time in Patent Office: 1,397 Days
• Field of Search: None
• US Class Current: 714/19
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 16/1865 Transactional file systems
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Concepts for enhancing operation of transaction-safe file allocation table systems are described. The concepts include writing a file to non-volatile memory media and rendering an update of file size to the TFAT storage medium; and receiving a request to locate data in a non-volatile memory having a TFAT file management system, selecting a sector of the memory to parse to locate the data, determining when the selected sector is a first sector of a directory or subdirectory of the memory and when determining reveals that the selected sector is a first sector, skipping reading data from the selected sector. The concepts also include flushing a cache and synchronizing FATs.

Claims

1. A process for maintaining multiple transaction-safe file allocation tables (TFATs) for a volume of TFAT storage medium, comprising:

writing a file to non-volatile memory media;

rendering an update of file size to at least one of the multiple TFATs maintained for the TFAT storage medium;

synchronizing the at least one updated TFAT with at least one other TFAT for the TFAT storage medium such that at least two of the multiple TFATs are copies of one another; and

changing a variable to a predetermined value to indicate that one of the synchronized TFATs is designated an active TFAT and that another of the synchronized TFATs is designated an inactive TFAT.

2. The process of claim 1, wherein the TFAT storage medium comprises at least one non-volatile solid state memory device.

3. The process of claim 1, further comprising, prior to writing to non-volatile storage media, storing data to be written in a cache memory, and, subsequent to transacting an atomic memory write, flushing the cache memory.

4. The process of claim 1, wherein an atomic memory write includes writing multiple discontinuous pages to be written to discontinuous locations.

5. The process of claim 1, further comprising:

determining when an atomic write includes writing new data over at least a portion of an entire cluster; and

when determining indicates that the entire cluster will be re-rewritten, writing the new data over a new cluster without first re-writing old data in the new cluster location.

6. The process of claim 1, wherein rendering file size transaction safe is done when the TFAT storage medium is specifically configured to make file size data transaction safe.

7. The process of claim 1, wherein writing comprises performing an atomic memory write via block drivers.

8. The process of claim 1, wherein writing comprises writing multiple discontinuous pages to discontinuous locations of a file.

9. A process for maintaining transaction-safe file allocation tables (TFATs) for a volume of TFAT storage medium, comprising:

determining when a write request includes need for writing new data over at least a portion of an entire cluster;

when determining indicates that the entire cluster will be rewritten, writing the new data over the new cluster without first re-writing old data in the new cluster location;

rendering an update to one of a plurality of TFATs maintained for the TFAT storage medium in response to writing any new data, the updated TFAT designated an inactive TFAT prior to the rendering;

copying the updated TFAT over another one of the plurality of TFATs; and

flipping the state of a bit to indicate that the updated TFAT is designated an active TFAT after the rendering.

10. The process of claim 9, further comprising, when determining indicates that the cluster will not be rewritten, maintaining that cluster and continuing with the write request.

11. The process of claim 9, wherein writing the new data over the new sector of the storage medium comprises atomically writing the data to the new sector via block drivers.

12. A process for writing data to a file in a TFAT volume, comprising:

writing multiple discontinuous pages to discontinuous locations of the file;

rendering an update to a first TFAT maintained for the TFAT volume, the first TFAT designated as inactive prior to the rendering the update;

changing a bit setting to designate the first TFAT as active after the rendering the update; and

synchronizing the first TFAT with a second TFAT maintained for the TFAT volume such that the first and second TFATs are copies of one another, wherein the changing the bit setting further designates the second TFAT as inactive.

13. The process of claim 12, wherein writing comprises writing atomically via a block driver.

14. The process of claim 12, wherein writing comprises performing an atomic write.

15. The process of claim 12, wherein the file was opened in a write-through mode.

16. Computer readable storage media including computer-readable instructions configured to cause one or more processors to:

open a file for writing in a write-through mode;

first write a first page of data to a first location in the file within a TFAT volume;

second write a second page of data to a second location in the file within the TFAT volume, the second location being discontinuous with the first location, wherein the first and second write comprise an atomic write;

render an update to a first TFAT maintained for the TFAT volume in response to the first write and the second write;

copy the first TFAT over a second TFAT maintained for the TFAT volume in response to rendering the update; and

changing a bit setting so as to designate the first TFAT as active and the second TFAT as inactive.

17. The computer readable storage media of claim 16, wherein the computer readable instructions further comprise instructions to cause the one or more processors to flush a cache memory in conjunction with the first and second writes.

18. The computer readable storage media of claim 16, wherein the computer readable instructions further comprise instructions to cause the one or more processors to first and second write the first and second pages to a non-volatile memory.

19. The computer readable storage media of claim 16, wherein the computer readable instructions further comprise instructions to cause the one or more processors to first and second write the first and second pages to a non-volatile solid-state memory.

20. The computer readable storage media of claim 16, wherein the computer readable instructions further comprise instructions to cause the one or more processors to first and second write the first and second pages from a volatile memory to a flash memory.