FILE SYSTEM AND METHOD OF FILE ACCESS

• US 20100332534A1
• Filed: 06/30/2009
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: CHANG, ROBERT, QAWAMI, BAHMAN, TANIK, HALUK, YUAN, PO, LIU, XIAN JUN
• Granted Patent: US 8,645,438 B2
• Time in Patent Office: Days
• US Class Current: 707/770
• CPC Class Codes: G06F 16/13 File access structures, e.g. distributed indices arrangements of input from, or output to, record carriers G06F3/06
• CPC Class Codes: G06F 16/1847 specifically adapted to static storage, e.g. adapted to flash memory or SSD

Abstract

A file system and method of file access are disclosed. In a particular embodiment, a method is performed at a host device coupled to a non-volatile memory, where the host device includes a memory having a first file data structure. A first directory entry in a file directory of a file system is located where the first directory entry corresponds to a first file stored in the non-volatile memory. First data associated with the first directory entry, including first location data indicating a location of the first file in the non-volatile memory, is retrieved and stored in the first file data structure. A request to open the first file is received. In response, the first location data of the first file is retrieved from the first file data structure and data of the first file from the non-volatile memory is read. First metadata associated with the first file is extracted from the data read from the non-volatile memory.

Claims

1. A method, comprising:

at a host device coupled to a non-volatile memory, the host device including a memory having a first file data structure,

receiving a request to open a first file; and

in response to the request to open the first file;

retrieving first location data of the first file from the first file data structure;

reading data of the first file from the non-volatile memory; and

extracting first metadata associated with the first file from the data read from the non-volatile memory.

2. The method of claim 1, further comprising storing the first metadata in a metadata table.

3. The method of claim 2, further comprising storing a copy of the metadata table to the non-volatile memory.

4. The method of claim 1, wherein the request to open the first file includes an open file command having an identifier of a file to be opened.

5. The method of claim 4, further comprising:

comparing the identifier to an identifier stored at the first file data structure; and

one of;

providing the first location data of the first file when the identifier of the file to be opened is the same as the identifier stored at the first data structure; and

scanning the file directory until finding a directory entry listing the identifier of the file to be opened.

6. The method of claim 1, further comprising:

locating a first directory entry in a file directory of a file system, wherein the first directory entry corresponds to the first file stored in the non-volatile memory;

retrieving first data associated with the first directory entry, wherein the first data includes the first location data indicating a location of the first file in the non-volatile memory; and

storing the first data in the first file data structure.

7. The method of claim 6, further comprising:

locating a second directory entry in the file directory of the file system, wherein the second directory entry corresponds to a second file stored in the non-volatile memory;

retrieving data associated with the second directory entry, wherein the data includes second location data indicating a location of the second file in the non-volatile memory; and

storing the second data in a second file data structure at the memory.

8. The method of claim 7, wherein the second directory entry is a next sequentially stored directory entry following the first directory entry and wherein the next sequentially stored directory entry is identified in response to a get next file command.

9. The method of claim 8, wherein the second file has a media type that is a same media type as the first file.

10. The method of claim 9, wherein the media type includes an audio file type.

11. The method of claim 7, further comprising, upon receiving a request to open the second file, transferring content of the second file data structure to the first file data structure.

12. The method of claim 7, further comprising, upon receiving a request to open the second file, re-designating the second file data structure as the first file data structure.

13. The method of claim 6, further comprising, prior to locating the first directory entry, copying at least a portion of the file directory to the memory at the host device.

14. The method of claim 1, wherein the first file includes one of:

an audio recording file;

an image file; and

an audiovisual recording file.

15. A method comprising:

at a host device coupled to a non-volatile memory, the host device including a memory having a first file data structure and a second file data structure,

in response to a request to open a first file;

retrieving first location data of the first file from the first file data structure;

reading data of the first file at a first location of the non-volatile memory;

locating a second directory entry in the file directory, wherein the second directory entry corresponds to a second file, and wherein the second directory entry is identified by a get next file operating system command;

retrieving second data associated with the second directory entry, wherein the second data includes second location data indicating a location of the second file in the non-volatile memory; and

storing the second data in the second file data structure.

16. The method of claim 15, further comprising:

receiving a request to access the first file that is stored in the non-volatile memory;

locating a first directory entry in a file directory of a file system wherein the first directory entry corresponds to the first file;

retrieving first data associated with the first directory entry, wherein the first data includes the first location data indicating the first location of the first file in the non-volatile memory;

storing the first data in the first file data structure;

17. The method of claim 15, further comprising:

extracting first metadata corresponding to the first file; and

storing the first metadata in a metadata table in the memory.

18. The method of claim 17, further comprising storing a copy of the metadata table to the non-volatile memory.

19. The method of claim 15, wherein the request to open the first file comprises an open file command that includes an identifier of a file to be opened.

20. The method of claim 19, further comprising:

comparing the identifier to an identifier stored at the first file data structure; and

one of;

providing the first location data of the first file when the identifier of the file to be opened is the same as the identifier stored at the first data structure; and

scanning the file directory until finding a directory entry listing the identifier of the file to be opened.

21. The method of claim 15, wherein the second file has a media type that is a same media type as the first file.

22. The method of claim 15, further comprising, prior to locating the first directory entry, copying at least a portion of the file directory to the memory at the host device.

23. A host device, comprising:

a non-volatile memory interface to receive a non-volatile memory storing a plurality of data files and a file directory;

a memory storing a first file data structure; and

a file opener configured to compare a file identifier received via a file open command to a first identifier in the first file data structure and to initiate a search of the file directory at the non-volatile memory when the file identifier is not the same as the first identifier in the first file data structure.

24. The host device of claim 23, wherein the file opener is further configured to retrieve the first identifier from a first directory entry in the file directory with one of a get first command to access a directory entry appearing first in the file directory and a get next command to access a next directory entry in the file directory and to store the first identifier in the first file data structure.

25. The host device of claim 24, further comprising a second file data structure stored at the memory.

26. The host device of claim 25, wherein the file opener is further configured to retrieve a second identifier from a second directory entry in the file directory with the get next command to access the next directory entry following the first directory entry and to store the second identifier in a second file data structure.

27. The host device of claim 26, wherein, before initiating the search of the directory of files at the non-volatile memory, the file opener is further configured to compare the file identifier received via the file open command to the second identifier in the second file data structure.

28. The host device of claim 24, further comprising a metadata table builder configured to access a first file associated with the first identifier stored in the first data structure, extract metadata corresponding to the first file, and store the metadata in a metadata table stored at the memory of the host device.

29. The host device of claim 28, wherein the metadata table builder is further configured to cause the file opener to issue a get next command to access the next directory entry in the file directory and to store a next identifier associated with the next directory entry in the file directory.

30. The host device of claim 28, wherein the metadata table builder is further configured to store a copy of the metadata table at the non-volatile memory.

31. The host device of claim 23, wherein the non-volatile memory receivable by the non-volatile memory interface includes a removable non-volatile memory.

32. The host device of claim 23, further comprising:

a portable computer;

a wireless telephone;

a wireless network device;

a media player;

a game device; and

a digital camera.