File system and method of file access

• US 8,645,438 B2
• Filed: 06/30/2009
• Issued: 02/04/2014
• 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, Yuan, Po, Liu, Xian Jun, Qawami, Bahman, Tanik, Haluk
• Primary Examiner(s): Le, Debbie
• Assistant Examiner(s): Mobin, Hasanul
• Application Number:
  US12/495,450
• Publication Number:
  US 20100332534A1
• Time in Patent Office: 1,680 Days
• Field of Search: None
• US Class Current: 707/829
• 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:

receiving, at a host device coupled to a non-volatile memory device, a request to open a first file stored in the non-volatile memory device, the host device including a memory that is distinct from the non-volatile memory device and that stores a first file data structure and a second file data structure; and

in response to the request to open the first file;

retrieving, by the host device, first location data of the first file from the first file data structure stored in the memory of the host device;

reading, by the host device, data of the first file at a first location of the non-volatile memory device, the first location identified based on the retrieved first location data;

locating, by the host device, a second directory entry in a 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, by the host device, 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 device; and

storing, by the host device, the second data in the second file data structure.

2. The method of claim 1, further comprising:

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

locating a first directory entry in the file directory, 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 device; and

storing the first data in the first file data structure.

3. The method of claim 1, further comprising:

extracting first metadata corresponding to the first file; and

storing the first metadata in a metadata table in the memory of the host device.

4. The method of claim 3, further comprising copying the metadata table from the memory of the host device to the non-volatile memory device, wherein the metadata table is copied from the non-volatile memory device to a second host device when the non-volatile memory device is coupled to the second host device.

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

6. The method of claim 5, 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.

7. The method of claim 1, wherein the second file has a media type that is a same media type as the first file.

8. The method of claim 2, 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.

9. The method of claim 2, 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 the get next file operating system command.

10. The method of claim 1, 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.

11. The method of claim 1, further comprising, upon receiving a request to open the second file, re-designating the second file data structure as the first file data structure.

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

an audio recording file;

an image file; and

an audiovisual recording file.

13. The method of claim 7, wherein the media type includes an audio file type.

14. A host device, comprising:

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

a memory internal to the host device and distinct from the removable non-volatile memory device, the memory storing a first file data structure and a second file data structure; and

a file opener configured to, in response to a command to open a file having a file identifier;

when the file identifier is found in the first file data structure, access the file based on an address stored in the first file data structure;

when the file identifier is not found in the first file data structure;

initiate a search of the file directory at the removable non-volatile memory device to identify a first identifier matching the file identifier;

retrieve the first identifier from a first directory entry in the file directory;

store the first identifier in the first file data structure;

retrieve a second identifier from a second directory entry in the file directory using a get next command; and

store the second identifier in the second file data structure.

15. The host device of claim 14, 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.

16. The host device of claim 15, wherein the metadata table builder is further configured to cause the file opener to issue the get next command to access the second directory entry in the file directory, access a second file associated with the second identifier, extract second metadata corresponding to the second file, and store the second metadata in the metadata table.

17. The host device of claim 15, wherein the metadata table builder is further configured to copy the metadata table from the memory of the host device to the removable non-volatile memory device, and wherein the metadata table is copied from the removable non-volatile memory device to a second host device when the non-volatile memory device is coupled to the second host device.

18. The host device of claim 14, further comprising:

a portable computer;

a wireless telephone;

a wireless network device;

a media player;

a game device;

or

a digital camera.