Method and apparatus for managing file system

• US 9,286,213 B2
• Filed: 09/18/2013
• Issued: 03/15/2016
• Est. Priority Date: 09/20/2012
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Chun, Han Sung
• Primary Examiner(s): Le, Uyen
• Application Number:
  US14/030,455
• Publication Number:
  US 20140082031A1
• Time in Patent Office: 909 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 16/1847 specifically adapted to static storage, e.g. adapted to flash memory or SSD

Abstract

A file management system for managing a file using a logical erase block (LEB) corresponding to a physical erase block (PEB). The file management system includes a free LEB list storing a free LEB allowing writing on all pages; a dirty LEB list storing a dirty LEB that is not the free LEB; and an obsolete area determining module determining an obsolete area in at least one dirty LEB, by referring to a block table storing information about whether or not at least one block is being used and according to whether or not the at least one dirty LEB is mapped to a PEB.

Claims

1. An apparatus for managing a file using a logical erase block corresponding to a physical erase block, the apparatus comprising:

a block allocating module receiving available blocks of at least one free logical erase block stored in a free logical erase block list and transmits the available blocks to a write module, the at least one free logical erase block allowing writing on all pages;

a garbage collecting module receiving at least one dirty logical erase block stored in a dirty logical erase block list and sends the at least one dirty logical erase block to an obsolete area determining module, the at least one dirty logical erase block is not the at least one free logical erase block;

the write module to which is allocated, if an update write request for correcting existing data in a block of the at least one dirty logical erase block is received, one of the available blocks from the block allocating module, and writing information in a block table indicating that the block of the at least one dirty logical erase block is no longer used; and

the obsolete area determining module receiving the at least one dirty logical erase block from the garbage collecting module to determine an obsolete area in the at least one dirty logical erase block, by referring to the block table storing information about whether or not at least one block of the at least one dirty logical erase block is being used and according to whether or not the at least one dirty logical erase block is mapped to a physical erase block, and transmits the determination to the garbage collecting module.

2. The apparatus of claim 1, wherein the garbage collecting module collects garbage for the at least one dirty logical erase block included in the dirty logical erase block list, according to the result of the determination of the obsolete area.

3. The apparatus of claim 2, wherein the garbage collecting module classifies blocks included in the at least one dirty logical erase block included in the dirty logical erase block list into an obsolete area and a valid area, copies the valid area to another free logical erase block, erases the at least one dirty logical erase block which has only the obsolete area remaining, and moves the at least one dirty logical erase block to the free logical erase block list.

4. The apparatus of claim 3, wherein the garbage collecting module releases mapping between a logical erase block including an existing obsolete area, moved to the free logical erase block list, and a physical erase block.

5. The apparatus of claim 1, wherein the block allocating module sequentially provides available blocks based on the free logical erase block list, and moves a logical erase block having no available space to the dirty logical erase block list.

6. The apparatus of claim 1,

wherein the block is a block which has already been allocated and the one of the available blocks is a newly allocated block.

7. The apparatus of claim 1, wherein the obsolete area determining module checks whether individual blocks constituting a dirty logical erase block are being used by referring to the block table, and if a block is not being used, the obsolete area determining module determines the block as an obsolete block, and if a block is being used, the obsolete area determining module determines the block as a valid block.

8. The apparatus of claim 1, wherein the block table is stored in a metadata storage area.

9. The apparatus of claim 1, wherein a number of physical erase blocks included in a physical memory is greater than or equal to a number of logical erase blocks.

10. The apparatus of claim 1, wherein each physical erase block comprises an erase counter including information regarding a number of times that the corresponding physical erase block has been erased.

11. The apparatus of claim 10, wherein the erase counter is used for wear-leveling by a logical erase block layer.

12. A computer implemented method of managing a file system using a logical erase block corresponding to a physical erase block, the method comprising:

receiving available blocks of at least one free logical erase block stored in a free logical erase block list;

if an update write request for correcting existing data in a block of at least one dirty logical erase block is received;

allocating one of the available blocks of the at least one free logical erase block, and

writing information in a block table indicating that the block of the at least one dirty logical erase block is no longer used;

determining an obsolete area in the at least one dirty logical erase block, by referring to the block table storing information about whether or not at least one block of the at least one dirty logical erase block is being used and according to whether or not the at least one dirty logical erase block is mapped to a physical erase block; and

performing garbage collection for the at least one dirty logical erase block according to the result of the determination of the obsolete area,

wherein the at least one free logical erase block is a logical erase block allowing writing on all pages, and the at least one dirty logical erase block is a logical erase block that is not the at least one free logical erase block.

13. The method of claim 12, wherein the performing of the garbage collection for the at least one dirty logical erase block comprises:

classifying the at least one dirty logical erase block into an obsolete area and a valid area;

copying the valid area to another free logical erase block;

erasing the at least one dirty logical erase block which has only the obsolete area remaining; and

moving the at least one dirty logical erase block to the free logical erase block list.

14. The method of claim 13, further comprising releasing mapping between a logical erase block including an existing obsolete area, moved to the free logical erase block list, and physical erase block.

15. The method of claim 12,

wherein the block of the at least one dirty logical erase block is a block which has already been allocated and the one of the available blocks is a newly allocated block.

16. The method of claim 12, wherein the determining of the obsolete area for the at least one dirty logical erase block comprises:

checking whether individual blocks constituting the at least one dirty logical erase block are being used by referring to the block table; and

determining a corresponding block as an obsolete block if the block is not being used, and determining the block as a valid block if the block is being used.