Flash translation layer block indication map revision system and method

• US 6,014,724 A
• Filed: 09/17/1996
• Issued: 01/11/2000
• Est. Priority Date: 10/27/1995
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: SCM Microsystems US Incorporated (Identive Group Incorporated)
• Inventors: Jenett, Detlef
• Primary Examiner(s): Cabeca, John W.
• Assistant Examiner(s): Verbrugge, Kevin
• Application Number:
  US08/710,463
• Time in Patent Office: 1,211 Days
• Field of Search: 395/412, 395/442, 395/430, 395/481, 711/202, 711/115, 711/103, 711/154
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7209 Validity control, e.g. using flags, time stamps or sequence numbers
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• 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]

Abstract

A system and method of avoiding preservation of files deleted in a flash memory by indicating deletion in a File Indication Map without modifying an associated block allocation map controls transfer of files from a full flash memory erase unit to a transfer flash memory erase unit. Modified File Indication Maps are compared with prior File Indication Maps to establish file deletion and to control modification of an associated block allocation map. The prior File Indication Map in flash memory is updated after comparison is completed.

Claims

1. A flash memory system, comprising:

a flash memory having a plurality of sectors, said flash memory storing status information indicating the status of said sectors;

storage, residing within said flash memory, for storing a set of file information, said file information including mapping information, in the form of a file indication map residing in a file system used by an operating system controlling said storing of the file information, for mapping a file to one or more of said sectors, wherein a copy of the file indication map residing in the file system used by the operating system is made in a flash translation layer separately from said file indication map residing in the file system, thereby providing a status record of a former file indication map for comparison against subsequent modifications of the file indication map residing in the file system used by the operating system; and

an agent for receiving a set of updated file information from said file system, said agent determining whether there is a difference between said updated file information and said file information, and if so, altering the status information for selected sectors of said flash memory to reflect said difference.

2. The system of claim 1 including a flash translation layer for interfacing said flash memory with said file system.

3. The system of claim 2 wherein said flash translation layer includes said agent.

4. The system of claim 2 wherein the flash translation layer includes the storage for storing said file information.

5. The system of claim 1, wherein said status information includes a block allocation map.

6. The system of claim 5, wherein if a discrepancy is noted between the mapping information residing within the flash memory and said file indication map, updating the block allocation map to delete the association between a physical location at which the identified deleted file was stored and a virtual address formerly connected with the particular physical location, said particular physical location associated with physical sectors of the flash medium with a related virtual address.

7. The system of claim 6, wherein after a file is deleted, the sector of flash memory referred to in the block allocation map is indicated as other than valid, preventing preservation by transfer out to a transfer unit prior to erase, thereby resulting in complete erasure of said sector during the erase operation.

8. The system of claim 7, wherein determination is made by comparing the mapping information residing within the flash memory and said file information map, and replacement is made after said comparison.

9. The system of claim 1, wherein said status information includes a virtual map table.

10. The system of claim 1, wherein determination is made by comparing the mapping information residing within the flash memory and said file indication map, and replacement is made after said comparison.

11. Method of storing data in a flash memory system, the method comprising:

providing a flash memory having a plurality of sectors;

storing status information in the flash memory indicating the status of said plurality of sectors;

storing a set of file information on said flash memory in a storage location residing within said flash memory, including mapping information, in the form of a file indication map residing in a file system used by an operating system controlling said storing of the file information, for mapping a file to one or more of said sectors; and

receiving a set of updated file information from said file system, and determining whether there is a difference between said updated file information and said file information, and if so, altering the status information for selected sectors of said flash memory to reflect said difference, wherein a copy of the file indication map residing in the file system used by the operating system is made in a flash translation layer separately from said file indication map residing in the file system, thereby providing a status record of a former file indicator map for comparison against subsequent modifications of the file indication map residing in the file system used by the operating system.

12. The method of claim 11 including using a flash translation layer for interfacing said flash memory with said file system.

13. The method of claim 12 wherein said flash translation layer includes an agent for receiving a set of updated file information from said file system, said agent determining whether there is a difference between said updated file information and said file information, and if so, altering the status information for selected sectors of said flash memory to reflect said difference.

14. The method of claim 12 wherein the flash translation layer includes the storage for storing said file information.

15. The method of claim 11, wherein said status information includes a block allocation map.

16. The method of claim 15, wherein if a discrepancy is noted between the mapping information residing within the flash memory and said file indicatioh map, updating the block allocation map to delete the association between a physical location at which the identified deleted file was stored and a virtual address formerly connected with the particular physical location, said particular physical location associated with physical sectors of the flash medium with a related virtual address.

17. The method of claim 16, wherein after a file is deleted, the sector of flash memory referred to in the block allocation map is indicated as other than valid, preventing preservation by transfer out to a transfer unit prior to erase, thereby resulting in complete erasure of said sector during the erase operation.

18. The method of claim 17, wherein determination is made by comparing the mapping information residing within the flash memory and said file indication, and replacement is made after said comparison.

19. The method of claim 11, wherein said status information includes a virtual map table.

20. The method of claim 11, wherein determination is made by comparing the mapping information residing within the flash memory and said file indication map, and replacement is made after said comparison.

21. Method of storing data in a flash memory system, the method comprising:

providing a flash memory having a plurality of sectors;

storing status information, including a block allocation map, in the flash memory indicating the status of said plurality of sectors;

storing a set of file information on said flash memory in a storage location residing within said flash memory, including mapping information, in the form of a file indication map residing in a file system used by an operating system controlling said storing of the file information, for mapping a file to one or more of said sectors; and

receiving a set of updated file information from said file system, and determining whether there is a difference between said updated file information and said file information, and if so, altering the status information for selected sectors of said flash memory to reflect said difference, wherein

if a discrepancy is noted between the mapping information residing within the flash memory and said file indication map, updating the block allocation map to delete the association between a physical location at which the identified deleted file was stored and a virtual address formerly connected with the particular physical location, said particular physical location associated with physical sectors of the flash medium with a related virtual address, after a file is deleted,

the sector of flash memory referred to in the block allocation map is indicated as other than valid, preventing preservation by transfer out to a transfer unit prior to erase, thereby resulting in complete erasure of said sector during the erase operation, said determination made by comparing the mapping information residing within the flash memory and said file indication map, and replacement is made after said comparison, and

a copy of the file indication map residing in the file system used by the operating system is made in a flash translation layer separately from said file indication map residing in the file syst m,thereby providing a status record of a former file indication map for comparison against subsequent modifications of the file indication map residing in the file system used by the operating system.

22. A flash memory system, comprising:

a flash memory having a plurality of sectors, said flash memory storing status information indicating the status of said sectors, said status information including a block allocation map;

storage, residing within said flash memory, for storing a set of file information, said file information including mapping information, in the form of a file indication map residing in a file system used by an operating system controlling said storing of the file information, for mapping a file to one or more of said sectors; and

an agent for receiving a set of updated file information from said file system, said agent determining whether there is a difference between said updated file information and said file information by comparing the mapping information residing within the flash memory and said file indication map, and if so, altering the status information for selected sectors of said flash memory to reflect said difference, wherein

if a discrepancy is noted between the mapping information residing within the flash memory and said file indication map,

the block allocation map is updated to delete the association between a physical location at which the identified deleted file was stored and a virtual address formerly connected with the particular physical location, said particular physical location associated with physical sectors of the flash medium with a related virtual address,

after a file is deleted, the sector of flash memory referred to in the block allocation map is indicated as other than valid, preventing preservation by transfer out to a transfer unit prior to erase, thereby resulting in complete erasure of said sector during the erase operation,

replacement is made after said comparison, and

a copy of the file indication map residing in the file system used by the operating system is made in a flash translation layer separately from said file indication map residing in the file system, thereby providing a status record of a former file indication map for comparison against subsequent modifications of the file indication map residing in the file system used by the operating system.