KR20010037155A - Flash file system - Google Patents

Abstract

PURPOSE: The flash file system is provided to easily access data in a form of a file, even though using a special file system is difficult, by forming an independent file system in a flash memory. CONSTITUTION: A deletion block is a group of continuous data which may be deleted in a flash memory at a time. There are three types of deletion block, that is, a file information block(101), a free deletion block(102) and a data block(103). One file information block(101) and one free deletion block(102) exist in a flash file system. The other blocks are assigned to the data block(103). A state, a boot record and a plurality of file information items are recorded in the file information block(101). The free deletion block(102) is used for correcting the file information block(102). Data of a file are recorded in the data block(103).

Description

Flash file system {FLASH FILE SYSTEM}

The present invention relates to a flash file system, and more particularly, to manage the flash file system independently without the need for a separate operation program, thereby managing data in a file unit in the flash file system (creation and recording, modification, retrieval, It relates to a flash file system that can be deleted, restored, etc.).

Flash memory, a type of EEPROM (Electronically Erasable and Programmable Read Only Memory) using a flash type floating gate transistor, is widely used as a program and data storage device for a computer and a mobile communication terminal.

Unlike conventional memory, flash memory can record and delete data only by simple program control, and its use area is rapidly expanding due to the characteristic that stored data is preserved even when power is cut off.

Meanwhile, the flash memory can randomly access data stored in a specific location like the conventional random access memory (RAM), nonvolatile storage (NVRAM), magnetic disk, and the like. It takes a different way from the medium.

The related art of the conventional flash file system is presented in US Patent Publication No. 5,404,485 (1995.04.04), and the related art of the conventional flash file system will be described with reference to FIG. 1 as follows.

FIG. 1 is a diagram showing a virtual memory map structure for writing data to a conventional flash memory.

As shown in FIG. 1, a virtual mapping technique should be used to access data recorded in a flash memory. Each byte in a conventional flash memory is given a physical address (10) and a virtual address (20). The virtual memory map is responsible for the translation between the physical address 10 and the virtual address 20.

On the other hand, bytes having a physically contiguous address are called blocks, and contiguous blocks gather to form a unit. A unit is an erase block that can be physically erased from flash memory at once. Each unit is assigned a logical unit number 30.

In the virtual memory map, the physical address 10 corresponding to each virtual block is stored and used to convert to the physical address 10 when accessed through the virtual address 20. Even if the physical address 10 of the virtual block is changed, the changed physical address 10 is recorded in the virtual memory map, so that the same virtual address 20 can be continuously accessed.

When performing a read operation using the conventional flash file system, the virtual address 20 requested by the user is converted into the virtual block number 40 and the byte position in the block, which in turn uses the virtual memory map. Is converted into a physical address (10). A read operation is performed from this physical address 10.

In addition, the write operation is converted from the virtual address 20 to the physical address 10 through the virtual memory map as in the read operation. However, when data is already recorded in a block to be written, it is difficult to delete and rewrite only the block to be deleted because all of the units to which the block belongs, that is, the erase block, must be erased due to the characteristics of the flash memory. Therefore, the unused block is found, data is written to the block, and the virtual address 20 of the block is modified in the virtual memory map to be converted into the address 10 of the new physical block.

As the number of unused blocks in a unit decreases, the efficiency of use of the memory decreases. Therefore, only the used blocks are moved to another unit, and then all the corresponding units are deleted.

On the other hand, US Patent Publication No. 5,404,485 (1995.04.04) assigns a logical number 50 to a unit in another conventional embodiment, and converts it to a physical address 10, so that even if the data of the unit is moved, the same unit number The approach to access is provided.

However, according to such a conventional flash file system, the following problem (s) occur.

Conventionally, a method of writing data on a memory or reading data written in a flash memory using a virtual memory map is adopted. That is, in the related art, since the data access method is performed through the block number, the file unit access required by the actual application must be separately implemented or used in conjunction with another file system. However, it is inefficient to operate other file systems in an environment in which a storage medium other than a flash memory is not used or all the functions of a general file system are not required.

Accordingly, an object of the present invention is to solve such problem (s), and an object of the present invention is to construct an independent file system on a flash memory to easily access data in file units even in an environment in which a separate file system is difficult to use. To provide a flash file system.

In addition, another object of the present invention is to provide a flash file system that can recover even if a failure occurs while reading data from or writing data to the flash memory.

1 is a diagram showing a virtual memory map structure for writing data in a conventional flash memory;

2 is a view showing a flash file system according to the present invention,

3 is a detailed structural diagram of a file information block shown in FIG. 2;

4 is a detailed structural diagram of a file information item shown in FIG. 3;

5 is an operation flowchart showing a process of generating and writing a file through the flash file system of the present invention;

6 is an operational flowchart showing a process of performing a file modification through the flash file system of the present invention.

7 is a flowchart illustrating a process of performing a file reading operation through the flash file system of the present invention.

8 is a flowchart illustrating a process of performing a file deletion operation through the flash file system of the present invention.

9 is a flowchart illustrating a process of performing a file restoration operation through the flash file system of the present invention.

<Description of the code | symbol about the principal part of drawing>

101: file information block 102: free deletion block

103: data block 104: state of file information block

105: boot record 106: file information entry

107: State of file 109: Name of file

113: address (number) of data block

A feature of the present invention for achieving such object (s) comprises one file information block, one free erase block and at least one data block; The file information block includes a state indicating status information of the file information block, a boot record having an identifier of the file system, and at least one file information item on which information of a file recorded in the data block is recorded; The free delete block detects and stores only the ″ validated ″ file information items recorded in the file information block when updating the file information block, and stores the ″ validated ″ file information items stored after the file information block is deleted in the file information block. Send to update; At least one data block is written with data having consecutive addresses; When creating and recording a new file, assign a new file information item to the file information block, set the status of the new file information item to ″ creating ″, and record the information about the new file in the new file information item. At least one data block to which a new file is to be recorded, records the address of at least one data block allocated to the file information item, and writes a new file to the at least one data block and simultaneously displays the state of the file information item. Effective ″; When modifying an existing file, a new file information item is assigned, the information about the modified file is recorded in the assigned file information item, and at least one data block for recording the modified file is allocated to the file information item. After recording the address of at least one data block, the modified file is written to the at least one data block, and at the same time, the state of the new file information item is set to "valid", and any file information item related to the existing file before modification is changed. At the same time as the deletion, the status of the file information item is set to "delete"; When retrieving the contents of a file, any file information item corresponding to the contents of the file among the at least one file information item is detected, and the address of the at least one data block recorded in the detected file information item is found to find the address. Read data written to a data block of &lt; RTI ID = 0.0 &gt;; When the file is deleted, at least one data block associated with the file recorded in the detected file information item is set at the same time as detecting the file information item corresponding to the file and setting the state of the file information item to ″ deleting ″. It has a file system that finds an address and deletes the data recorded in the data block of the address and sets the status of the file information item to ″ delete ″.

Here, if the file system stops the operation while the contents of the file system are changed, the file system restarts the file system, searches for at least one file information item, and states the state of the file information item among the at least one file information item. It is preferable to detect file information items that are being deleted &quot; and &quot; creating &quot; to update the state of the detected file information items to &quot; delete &quot;.

The file information item may further include: a status indicating a current status of the file; Name of the file; And at least one address of at least one data block on which the file is recorded.

The data block preferably includes a block use map in the form of a bit map indicating whether the data block is used.

Hereinafter, exemplary embodiment (s) of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description there are shown a number of specific details, such as components of the specific circuit, which are provided only to help a more general understanding of the present invention that the present invention may be practiced without these specific details. It is self-evident to those of ordinary knowledge in Esau. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 is a diagram showing a flash file system according to the present invention, FIG. 3 is a detailed structural diagram of the file information block shown in FIG. 2, and FIG. 4 is a detail of the file information item shown in FIG. A structural diagram is shown, and FIG. 5 is a flowchart illustrating a process of performing a file generation and a recording operation through the flash file system of the present invention, and FIG. 6 is a file modification operation through the flash file system of the present invention. An operation flowchart showing a process is shown, and FIG. 7 is an operation flowchart showing a process of performing a file reading operation through the flash file system of the present invention, and FIG. 8 shows a file deleting operation through the flash file system of the present invention. An operation flow diagram illustrating a process of performing is illustrated, and FIG. 9 illustrates a flash file system of the present invention. An operation flowchart showing a process of performing a file restoration operation is shown.

First, the detailed structure of the flash file system of the present invention will be described with reference to FIGS. 2 to 4.

A set of consecutive data that can be erased at one time from a flash memory is called an erasure block. In the file system according to the present invention, the flash memory is managed in units of erase blocks. The size of the erase block may vary depending on the characteristics of the flash memory and the needs of the user.

As shown in FIG. 2, there are a file information block 101, a free deletion block 102, and a data block 103. As shown in FIG. There is one file information block 101 and one free erase block 102 in the flash file system, and the remaining blocks are allocated to the data block 103. In the file information block 101, as shown in FIG. 3, a status 104, a boot record 105, and a plurality of file information items 106 are recorded. Here, the free deletion block 102 is a block used to modify the file information block 101. In addition, data of the file is recorded in the data block 103.

At this time, in the state 104 of the file information block 101, information indicating the current state of the file information block 101, such as whether the file information block 101 has been deleted or can be recorded, is recorded. The boot record 105 records the identifier of the file system and other information. In the plurality of file information items 106, file information for each file is recorded. In each file information item 106, as shown in FIG. 4, the status 107 of the file and the size 108 of the file information item are shown. ), File name 109, file creation or last modification date and time 110, length of file data 111, file attribute 112, number 113 of data block 103 where file data is recorded, and the like. This includes.

Referring to Figures 5 to 9 with respect to the operation of the present invention having such a configuration as follows.

Flash file system operation is divided into items such as file creation and recording, modification, retrieval, deletion, and recovery from failure.

First, in the case of generating and recording a file as shown in FIG. 5, it is checked whether a new file information item 106 can be allocated to the file information block 101 (S1). If there is space to which the new file information item 106 is to be allocated (S2, S15), the space for the new file information item 106 is allocated (S3), and the information about the file information item 106 (status, Name, date, size, attribute, etc.) are recorded (S5). At this time, the state 107 of the file is displayed as ″ creating ″ (S4). Then, one unused data block 103 is allocated (S6 to S8) and its address is recorded in the file information item 106 (S9), and the file data is recorded in the corresponding data block 103 (S10). . In this case, in order to be able to recover even if a system failure occurs during various operations of the flash memory, the number 113 of the data block 103 in which the file data of the file information item 106 is recorded is first recorded. This file data should be recorded in the data block 103. When the address and file data of all data blocks 103 related to the file are recorded, the remaining file information (name, file size, etc.) is recorded (S11). At this time, if necessary or if the file size can be known in advance, the size of the file information item 106 may be recorded first. When all of these recording operations are completed, the state 107 of the file is switched to valid (S12).

On the other hand, a block usage map is used to easily find the data block 103 which is not used in the file system. The block use map is usually configured in the form of a bit map, and each bit of the block use map indicates whether the corresponding block is used. Therefore, the file system can easily search whether the corresponding block is used through the bits of the block usage map.

Next, as shown in FIG. 6, when the contents of the file are modified, the file information items are reassigned (S17 to S19 and S31), and the same process as the above-described file generation and recording process is performed ( S20 ~ S24). Then, after recording the number of the data block 103 in which the modified contents are written in the new file information item 106 (S25 to S27), the previous file information item 106 ″ deletes ″ the state 107 of the file. Change to (S28).

In addition, in the case of reading the contents of the file as shown in FIG. 7, the file information block 101 checks each file information item 106 (S33) and checks whether the requested file exists (S34). If the file exists, the number 113 of the data block 103 in the file information item 106 is detected and data is read from the data block 103 (S35). If the requested file does not exist as a result of checking each file information item 106, it is treated as an error (S36).

Then, as shown in FIG. 8, when the file is deleted, the state 107 of the file in the file information item 106 is set to ″ deleting ″ (S37), and all data blocks belonging to the file ( After deleting 103 (S38), the block usage map of the data block 103 is updated (S39). Thereafter, after deleting all the data blocks 103 and updating the block usage map, the state 107 of the file is set to &quot; delete &quot; to indicate that the file has been deleted (S40).

Meanwhile, as shown in FIG. 9, if the system is down or a failure occurs while the contents of the file system are changed, the structure of the file system is destroyed after the system is restarted. Therefore, the first time you use or restart the file system, you must first check its structure. At this time, the state 107 of the file in the file information item 106 is checked to see if there is an item whose state 107 is "creating" or "deleting" (S41). Here, if the state 107 of the file is ″ creating ″ (S42), a failure has occurred while generating the file. If the state 107 of the file is ″ deleting ″ (S43), the failure occurs while deleting the file. This means that these files are generated, and therefore, the files corresponding to both cases become unnecessary files. Accordingly, the state 107 of the file in the file information item 106 is changed to ″ deleting ″ (S44), and all data blocks 103 belonging to the file information item 106 are deleted (S45). Is completed, the state 107 of the file is changed to ″ delete ″ (S46).

On the other hand, when there are many items deleted in the file information block 101, the use efficiency of the flash memory is reduced, so that the file information items 106 can be arranged using the free deletion block 102. FIG. That is, the state 107 of the file in each file information item 106 is examined to retrieve only the corresponding file information item 106 whose state 107 is "valid" and moves it to the free delete block 102. Let's do it. This process is called ″ playback ″. Thereafter, after deleting each file information item 106 in the file information block 101, the ″ valid &quot; file information items 106 stored in the free deletion block 102 are again stored in the file information block 101. Move to. At this time, the file information block 101 is reproduced when there are many deleted file information items 106, and the data block 103 is reproduced only when the file is deleted or modified (FIGS. S13 to S15 and FIG. 6). S29-S31).

On the other hand, in order to change the state 104 of the file information block 101, the state value changing procedure may be set so that the data block 103 does not need to be deleted each time. For example, the state 104 of the file information block 101 is determined (FF). Delete (8F) Restore (4F) Deleting (2F) Recordable (OF) You can change it to the same procedure as Full (08).

Similarly, in order to change the state 107 of the file in the file information item 106, the state value changing procedure may be set such that there is no need to newly create the file information item 106 or delete the entire file information block 101. . For example, the file state 107 of the file information item 106 is not used (FF). Generating (8F) Effective (4F) Deleting (2F) Changes can be made with the same procedure as deletion (OF).

As described above, although the specific embodiment (s) have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiment (s) but should be defined by the claims below and equivalents thereof.

As a result, according to the flash file system according to the present invention, the following advantage (s) occurs.

That is, by configuring a unique file system on the flash memory, it is possible to easily access data in file units even in an environment in which a separate file system is difficult to use.

In addition, even when a failure occurs while reading data from or writing data to the flash memory, the destroyed file system can be easily restored according to the state information of the file system.

Claims (4)

One file information block, one free erase block, and at least one data block; The file information block includes a state indicating status information of the file information block, a boot record having an identifier of a file system, and at least one file information item on which information of a file recorded in the data block is recorded; The free deletion block detects and stores only the ″ valid ″ file information items recorded in the file information block when updating the file information block, and the ″ valid ″ file information items stored after the file information block is deleted. Transmits to the file information block to update; The at least one data block is written with data having consecutive addresses; When a new file is created and recorded, a new file information item is assigned to the file information block, the state of the new file information item is set to ″ creating ″, and information about the new file is changed to the new file information. Write to an item, receive at least one data block for recording the new file, record the address of the at least one data block allocated to the file information item, and then record the new file in the at least one data block. Simultaneously update the status of the file information item to &quot; valid &quot;; When modifying an existing file, a new file information item is allocated, information about the modified file is recorded in the allocated file information item, and at least one data block for recording the modified file is allocated to the file information item. After recording the address of the at least one data block assigned to the at least one data block, the modified file is written to the at least one data block, and at the same time, the state of the new file information item is set to "valid", and the existing file before modification is Simultaneously delete any associated file information item and set the state of the file information item to &quot; delete &quot;; When retrieving the contents of the file, any of the at least one file information item corresponding to the contents of the file is detected, and the address of at least one data block recorded in the detected file information item is detected. Find and read data written to the data block of the address; When the file is deleted, the file information item corresponding to the file is detected, the state of the file information item is set to ″ deleting ″, and at least one related to the file recorded in the detected file information item. The flash file system which finds the address of the above data block, deletes the data recorded in the said data block of the said address, and sets the state of the file information item to "delete". The method of claim 1, wherein the file system, If the operation is stopped while the contents of the file system are changed, restarting the file system, searching for the at least one file information item, and deleting the state of the file information item from the at least one file information item. And a file information item having a &quot; during &quot; and &quot; creating &quot; to update all detected state of the file information item to &quot; delete &quot;. The method of claim 2, wherein the file information item, A status indicating the current state of the file; The name of the file; And And the address of said at least one block of data in which said file is written. The method of claim 2, wherein the data block, And a block use map in the form of a bit map indicating whether the data block is used.