File system and method of file access

• US 10,031,918 B2
• Filed: 12/23/2013
• Issued: 07/24/2018
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Chang, Robert, Yuan, Po, Liu, Xian Jun, Qawami, Bahman, Tanik, Haluk
• Primary Examiner(s): Mobin, Hasanul
• Application Number:
  US14/138,670
• Publication Number:
  US 20140108465A1
• Time in Patent Office: 1,674 Days
• 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 data storage device, where the host device includes a memory storing a file data structure. The host device receives a request to open a file and, in response to the request, retrieves location data of the file from the file data structure. The host device reads data of the file from the data storage device based on the location data and extracts metadata from the data of the file.

Claims

1. A method comprising:

receiving, from an application at a host device coupled to a data storage device, a request to open a first file of a plurality of files stored in the data storage device;

retrieving, by the host device in response to the request to open the first file, first location data of the first file from a file data structure of a plurality of file data structures stored in a memory of the host device, the memory distinct from the data storage device, each of the plurality of file data structures indicating a respective location at which a corresponding file of the plurality of files is stored in the data storage device;

issuing, by a file opener of a processor of the host device in response to the request to open the first file and prior to or without receiving a second request to open a next file of the plurality of files, a get next command to the memory to retrieve second location data of the next file, wherein the processor extracts metadata from the first file and copies metadata from a metadata table in the memory to the data storage device; and

initiating, by the processor, outputting of a data item associated with the first file from the host device to the data storage device based on the first location data.

2. The method of claim 1, wherein the processor extracts the metadata from the first file prior to initiating the outputting of the data item.

3. The method of claim 1, wherein:

the request to open the first file includes an open file command from an operating system at the host device,

the open file command includes an identifier of a particular file to be opened, and

the host device retrieves the first location data from the file data structure in response to determining that the identifier matches a second identifier stored in the file data structure.

4. The method of claim 1, further comprising:

generating at the host device a host file directory that corresponds to at least a portion of a first file directory stored at the data storage device; and

retrieving location data by scanning the host file directory in response to determining that an identifier of a file to be opened does not match any identifier stored in the file data structure.

5. The method of claim 1, further comprising:

locating a directory entry in a host file directory copied from a first file directory of the data storage device, wherein the directory entry corresponds to the first file stored in the data storage device;

retrieving the first location data from the directory entry; and

storing the first location data in the file data structure.

6. The method of claim 5, further comprising:

locating a second directory entry in the host file directory, wherein the second directory entry corresponds to the next file stored in the data storage device;

retrieving the second location data from the second directory entry, wherein the second location data indicates a location of the next file in the data storage device; and

storing the second location data in a second file data structure of the plurality of file data structures.

7. The method of claim 6, wherein:

the second directory entry is a next sequentially stored directory entry following the directory entry, and

the next sequentially stored directory entry is identified in response to receiving the get next command.

8. The method of claim 1, further comprising:

extracting the data item from the first file, wherein the data item is associated with the first file; and

opening, by the host device, the first file, wherein the first file is opened using the file data structure without performance of a file name search at the host device or at the data storage device.

9. The method of claim 1, further comprising, in response to receiving the second request to open the next file:

transferring content of a second file data structure of the plurality of file data structures to the file data structure;

or

re-designating the second file data structure as the file data structure.

13. The method of claim 1, further comprising:

in response to the first location data not being stored in the file data structure, accessing by the processor one of;

a second file data structure stored at the host device, the second file data structure configured to store second location data of a second file in the data storage device; and

a file directory, the file directory copied from the data storage device.

14. The method of claim 1, wherein:

the request to open the first file is received after a file directory is copied from the data storage device to the host device, and

the file directory is accessed after accessing a second file data structure of the plurality of file data structures and after determining that the first location data is not in the second file data structure.

15. The method of claim 1, further comprising:

storing the first location data in the file data structure prior to receiving the request to open the first file; and

storing the metadata in the metadata table, wherein the metadata stored in the metadata table is associated with the first file.

16. The method of claim 1, further comprising:

in response to the get next command, predictively fetching the second location data; and

after predictively fetching the second location data, receiving the second request to open the next file, wherein the get next command and the second request to open the next file are issued at the host device.

17. The method of claim 1, further comprising:

in response to receiving the request to open the first file;

reading data of the first file from the data storage device based on the first location data; and

retrieving the second location data from a second file data structure of the plurality of file data structures;

after receiving the request to open the first file, receiving the second request to open the next file; and

in response to the second request to open the next file, reading data of the next file from the data storage device based on the second location data.

10. A host device comprising:

a memory to store a plurality of file data structures, each of the plurality of file data structures indicating a respective location at which a corresponding file of a plurality of files is stored in a data storage device, the data storage device distinct from the memory;

a file opener to retrieve first location data of a first file from a file data structure of the plurality of file data structures in response to a request to open the first file stored in the data storage device and to cause issuance of a get next command to the memory to retrieve second location data of a next file of the plurality of files in response to the request to open the first file;

a table builder to extract metadata from the first file and to copy metadata from a metadata table in the memory to the data storage device; and

an interface to output a data item associated with the first file from the host device to the data storage device based on the first location data.

11. The host device of claim 10, wherein:

the file data structure is configured to enable the host device to open the first file without performance of a file name search at the host device or at the data storage device,

and the table builder is configured to store the data item in the metadata table.

12. The host device of claim 11, wherein:

the table builder is further configured to copy the metadata table from the host device to the data storage device, and

the metadata table is configured to be copied from the data storage device to a second host device in response to the data storage device being coupled to the second host device.

18. An apparatus comprising:

means for providing an interface to means for storing a plurality of files;

means for processing data, the means for processing data coupled to the means for providing and configured to;

receive a request to open a first file of the plurality of files;

retrieve, in response to the request to open the first file, first location data of the first file from a file data structure of a plurality of file data structures stored in a memory of the means for processing data, the memory distinct from the means for storing, each of the plurality of file data structures indicating a respective location at which a corresponding file of the plurality of files is stored in the means for storing;

issue, in response to the request to open the first file and prior to or without receiving a second request to open a next file of the plurality of files, a get next command to the memory to retrieve second location data of the next file;

extract metadata from the first file; and

copy metadata from a metadata table in the memory to the means for storing; and

means for outputting a data item associated with the first file from the means for processing data to the means for storing based on the first location data.

19. The apparatus of claim 18, wherein:

the means for processing data is configured to execute an application configured to issue the request to open the first file,

the get next command is issued by a file opener at the means for processing data, and

the first file and the next file have an audio file type.