Data area managing method in information recording medium and information processor employing data area managing

1. A data area managing method for an information recording medium, the method is used in an information processor that manages data stored in an information recording area in the information recording medium as file information, wherein

when said information processor accesses area management information that manages a free area state and link state of the information recording area in said information recording medium as the file information,

reading said file information of a first access size from said area management information when retrieving a free area from said area management information; and

reading said file information of a second access size smaller than the first access size from said area management information when retrieving link information from said area management information.

2. The data area managing method according to claim 1 , wherein said second access size is identical to a minimum reading and writing size of said information recording medium.

3. The data area managing method according to claim 1 , wherein two caches each having a different management block size are provided as area management information caches in said information processor, and by alternatively using said two caches for different purposes, at least one of said first access size and said second access size is changed according to the processing executed by said information processor.

4. The data area managing method according to claim 3 , wherein the processing executed by said information processor comprises:

a free area retrieval processing for retrieving a free area from said area management information; and

a link destination acquisition processing for acquiring a linked destination from said area management information.

5. The data area managing method according to claim 4 , wherein as an alternative use of said two area management information caches,

when said information processor executes said free area retrieval processing, said information processor uses a first area management information cache having a physical management block size determined from physical characteristics of said information recording medium or a size smaller than said first area management information cache, and

when said information processor executes said link destination acquisition processing, said information processor uses a second area management information cache smaller than said first area management information cache as an access unit of said information recording medium.

6. The data area managing method according to claim 5 , wherein said second area management information cache is used only for an exclusive processing for reading, and

said first area management information cache is used when information stored in said area management information is changed.

7. The data area managing method according to claim 1 , wherein said information recording medium is a NAND flash memory.

8. The data area managing method according to claim 1 , wherein said first access size is a size of an erase block which is determined from physical characteristics of said information recording medium.

9. The data area managing method according to claim 8 , wherein a size of said area management information is not a size of an integral multiple of the size of the erase block, and

said first access size of said area management information is less than said erase block size.

10. The data area managing method according to claim 1 , wherein said information processor provides a first cache for retrieving a free area referring to said area management information and a second cache for retrieving a link state referring to said area management information,

said information processor stores data of said first access size to said first cache read from said area management information, and

said information processor stores data of said second access size to said second cache read from said area management information.

11. An information processor which accesses an information recording medium that manages data stored in an information recording area by a file system comprising:

a FAT cache configured to read and store area management information which manages a free area state and link state of said information recording area from said information recording medium;

a volatile memory configured to hold data including: a start address of each block, location of the area management information stored in each block on said information recording medium, size of each block, and presence or absence of update, as FAT cache management information for managing said FAT cache by dividing said FAT cache into a plurality of blocks;

a FAT controller configured to refer to and update said FAT cache management information and controlling a read and change of said area management information to said FAT cache; and

a file system controller configured to access the area management information through said FAT cache controller and storing data in the information recording medium as a file, wherein

said FAT cache has at least one block having a first access size and at least one block having a second access size; and said second access size is smaller than said first access size;

wherein when said information processor accesses area management information that manages the free area state and the link state of the information recording area in said information recording medium as file information;

reading said file information of the first access size from said area management information when retrieving a free area from said area management information; and

reading said file information of the second access size smaller than the first access size from said area management information when retrieving link information from said area management information.

12. The information processor according to claim 11 , wherein said second access size is identical to a minimum reading and writing size of said information recording medium.

13. The information processor according to claim 12 , wherein said file system controller accesses a block having the first access size included in said FAT cache through said FAT cache controller when a free area retrieval processing for retrieving a free area from said area management information is performed, and accesses a block having the second access size included in said FAT cache through said FAT cache controller when a link destination acquisition processing for acquiring a linked destination from said area management information is performed.

14. An information processor for accessing an information recording medium having an information recording area and area management information that manages a free area state and a link state of the information recording area in said information recording medium, comprising:

an access unit that accesses said area management information in said information recording medium; and

a storing unit that stores data acquired through accessing,

wherein

said access unit reads data of a first access size from said area management information and stores data to said storing unit, when retrieving a free area from said area management information, and

said access unit reads data of a second access size smaller than said first access size from said area management information and stores data to said storing unit when retrieving link information from said area management information.

15. The information processor according to claim 14 , wherein

said second access size is identical to a minimum reading and writing size of said information recording medium.

16. The information processor according to claim 14 , wherein

said information recording medium is a NAND flash memory.

17. The information processor according to claim 14 , wherein

said first access size is a size of an erase block which is determined from physical characteristics of said information recording medium.

18. The information processor according to claim 17 , wherein

a size of said area management information is not a size of an integral multiple of the size of the erase block, and

said first access size of said area management information is less than said erase block size.

19. The information processor according to claim 14 , wherein said information processor provides a first cache for retrieving a free area referring to said area management information and a second cache for retrieving a link state referring to said area management information,

said information processor stores data of said first access size to said first cache read from said area management information, and

said information processor stores data of said second access size to said second cache read from said area management information.