JP2001175525A - File system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize the unnecessary address space of an EEPROM. SOLUTION: Concerning the file system for using an EEPROM 4 as a block device, this file system is provided with a file system managing part 2 for detecting a block corresponding to a user request and outputting a request by specifying the relation of a user request file and a block, a block address translating layer 3 for reporting request contents on the basis of the address of the EEPROM corresponding to the block of the user request from the file system managing part and applying processing corresponding to the request contents to the detected block by specifying the relation of the block and the address of the EEPROM or the like, and the page erasure type EEPROM 4 for recording the request contents reported from the translating means into a managing area by forming the managing area in one part of plural divided blocks or area except for these blocks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a file system which is suitable for an embedded computer having a small memory.

[0002]

2. Description of the Related Art Conventionally, a file system developed for a general system is often used for an embedded computer. In particular, the "FAT file system", which is a file system for microcomputers, is widely used because its implementation is simple and there are many commercially available software. Here, FAT (File Allo
The “cation table” means an area for storing position information of data stored on the disk. Therefore, F
An AT file system can be generally said to be a file system that stores and manages file names and addresses on a disk.

In recent years, a “page erasing type electrically erasable / writable read-only memory (hereinafter referred to as EEPRO)
M) is often used, but this EEPRO
M and the general purpose file system differ greatly in writing policy, for example, EEP as part of the file system.
When a ROM is used, it is necessary to ensure consistency.

Therefore, a general-purpose file system and an EEPR
FTL is a system for achieving consistency with OM.
(Flash Translation Layer) system has been developed. This FTL system uses a “page erase type EEPR
"OM" for "block device" for file system
It is a system that can be handled as.

[0005] By the way, when the FTL system is used,
There is no one-to-one correspondence between the blocks of the block device for the file system and the addresses on the EEPROM. The reason is that the general file system is premised on "rewriting" in block units, but EEPR
Even if the OM divides the EEPROM into blocks,
The rewriting of the EEPROM block is premised on "page erasure" which is a much larger unit than the block of the file system, and the upper limit number of repeated page erasures is set to a relatively low value (about 10 ⁵ ). Because it is. As a result, when an EEPROM is treated as a block device, not only is it impossible to erase a page unnecessarily, but also when a block of a block device is rewritten, each time the rewrite is performed, a different address from the previously written address on the EEPROM is used. The necessary information will be written.

[0006]

Therefore, in the file system using the FTL as described above, since the EEPROM is used for page erasure, even if it is unnecessary in the file system, it is written before when rewriting is performed. The block is retained. Therefore, when a user requests a file to be deleted or reduced, even if unnecessary blocks can be recorded as free information at the file system level,
The block on the EEPROM to be erased or reduced is kept as it is. Therefore, many blocks in the EEPROM remain used unless reused. The “unnecessary block” here means
Not only unnecessary at the file system level,
At the block device level, it is not possible to determine whether it is necessary or not, and only the last written information is always kept as the latest information.

Therefore, an EEPROM is used as a file system.
When there are many unnecessary blocks in the EEPROM, there is a disadvantage that the address space cannot be used effectively.
There is a problem that the writing speed to the block on M becomes slow.

The present invention has been made in view of the above circumstances, and actively creates an empty state at the flock device level for unnecessary blocks on a file system.
It is an object of the present invention to provide a file system capable of effectively utilizing an address space of an EEPROM and improving a writing speed of a block.

[0009]

Means for Solving the Problems (1) In order to solve the above-mentioned problems, a file system according to the present invention is a file system in which a page erase type EEPROM is divided into a plurality of blocks and used as a block device.
A relationship between a user request file and the block is defined, a file system management unit that detects a corresponding block when a user request is received and outputs a request, and a correspondence relationship between the block and an EEPROM address or the like is defined, A block requested by the user from the file system management unit is detected, and the EE corresponding to the detected block is detected.
A block address conversion means for notifying the contents of the request based on the address of the PROM and performing processing according to the contents of the request to the detection block; and a part of the plurality of divided blocks or an area other than these blocks. A management area is formed, and the EEPROM for recording the request content notified from the conversion means in the management area is provided.

According to the present invention having the above-described configuration, when a user makes a required request, the file system management unit detects a block corresponding to the user request file and sends the request content to the block device. Send out.
In the block address conversion means constituting a part of this block device, since the relationship between the block and the address of the EEPROM and the like is defined, the block of the content requested by the user is detected, and the address of the EEPROM is extracted from the detected block. , The request content is notified to the EEPROM, and processing corresponding to the request content is performed on the detection block.

Here, the EEPROM has a management area for recording information in a one-to-one relationship with the contents of the block address conversion means, and when a request content accompanied by an address is notified from the block address conversion means, the management area is managed. The request content is recorded in the corresponding area of the area. As a result, the file system management unit including the user uses the block address conversion means or the recorded contents of the management area of the EEPROM to
The empty state of the address space of the EEPROM can be known. For example, if there is an unnecessary mark which is the recording content added in the management area, a discard request or a rewrite request is made to a block adjacent to the unnecessary mark. Space can be increased, the page of the EEPROM can be erased, and the discarded address space of the EEPROM can be easily reused.

The file system management section simply has a function of passing input / output request data, and the relationship between the user request file and the block is defined between the file system management section and the block / address conversion means. In addition, when a user request is received, a block detection mechanism that detects a corresponding block and outputs the request may be provided.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of a file system according to the present invention.

The file system includes a user 1 who uses the file system, a file system management unit 2
, A block / address conversion layer 3 and an EEPR which is a page erasure type electrically erasable / writable read-only memory
OM4.

The user 1 has a function as a user interface, and generally has a user program. The user 1 has a function of, upon receiving a read / write request, a file erasing request, or a file moving request from the outside, converting the data into required data or the like in accordance with a user program and sending the converted data to the file system management unit 2.

The file system management unit 2 is a layer that provides files to the user 1 and makes various requests to a block device for handling the EEPROM 4 in the same manner as a magnetic disk. This is a layer that performs conversion between a block and a block of a block device.
The file system management unit 2 is provided with a table for handling a file system, such as a FAT.
This table stores and manages a file name according to the request from the user 1 and blocks to which the request is assigned. Therefore, the file system management unit 2
Has a function of detecting an allocated block when receiving a request content from the user 1 and transmitting the detected block number, the request content, and the like.

The block / address conversion layer 3 is a layer functioning as an interface of a block device for various requests from the file system management unit 2. The block / address conversion layer 3 is provided with a conversion table. And has the role of converting to command pairs.

The EEPROM 4 is divided into a plurality of blocks, and one block is formed in a size corresponding to, for example, a 512-byte area. Since a typical erase block of an EEPROM is 64 Kbytes,
The block of the block device of the EEPROM 4 and its area are greatly different. A management area 5 for holding data in a one-to-one relationship with the management contents of the conversion table of the conversion layer 3 is formed in some of the blocks formed in the EEPROM 4 or in an area other than the blocks.

Next, the operation of the above file system will be described.

Now, when a file discard request is output from the user 1, the file system management unit 2 does not need to hold the data for which the discard request has been received from the blocks pre-allocated to the table based on the file discard request. Block device (including the conversion layer)
Notify.

Here, the block / address conversion layer 3
When a block discard request is received, a process of stopping retaining unnecessary blocks from the conversion table (for example, an unnecessary marker adding process) is performed, and it is determined that the block has been discarded.
Notify EPROM4. The EEPROM 4 records an unnecessary marker on the block corresponding address management area in the management area 5 so as to maintain a one-to-one relationship with the conversion table of the block / address conversion layer 3. At this stage, E corresponding to the discarded block
Data is still stored in the data storage address of the EPROM.

However, since the conversion table and the management area 5 of the EEPROM 4 have a one-to-one relationship, for example, the user 1
Alternatively, if the file system management unit 2 requests the block / address conversion layer 3 or the like to write the contents of the conversion table, the EEPROM 4 which is the contents of the management area 5 of the EEPROM 4
Since the discarded address space of the OM4 can be easily grasped, for example, the EEP discarded through data rewriting
It is possible to increase the address space of the ROM 4.

This means that, for example, by rewriting data in an address space adjacent to a certain discarded address space, an address space corresponding to a page can be increased, and blocks corresponding to the page become unnecessary. At this time, if the page erasure is performed for the corresponding address of the EEPROM 4, a free area, and consequently, an effective use area or a reuse area can be increased in the address space of the EEPROM 4, and the page erasure is not performed until the area corresponding to the page is reached. , The number of erasures can be reduced.

In the above embodiment, the unnecessary tables are marked with unnecessary markers in the conversion table of the conversion layer 3 so that the user 1 or the like can grasp them. The user 1 or the like simply stops holding the conversion table or reads the contents of the management area 5 in the EEPROM 4 by the user 1 or the like, and collects the address space of the EEPROM 4 discarded by page erasure so that the address space becomes empty. Then, similarly, the discarded address space of the EEPROM 4 can be reused.

(Other Embodiments) FIG. 2 is a configuration diagram showing another embodiment of the file system according to the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this file system, in addition to the improvement of the file system management unit 2a, a block detection mechanism 6 is newly provided between the file system management unit 2a and the block / address conversion layer 3.

The main function of the file system management section 2a is to transfer a request between the user 1 and the block device, which is an original function of the file system.

The block detecting mechanism 6 has a table for storing a file name corresponding to the request from the user 1 described in FIG. 1 and a block to which the request is allocated. Is output, the block that is no longer required to hold the data for which the discard request has been received is detected from among the blocks allocated in advance to the table based on the file discard request passed from the file system management unit 2, and It has a function of notifying a block device (including a conversion layer) of a "block discard request" for a detected block.

Therefore, in this case, the file system management section 2a only passes the file discard request,
When receiving the file discard request, the block detection mechanism 6 detects a block of a block device that is not required from the table, and notifies the block device (including the conversion layer) of a “block discard request” for the detected block. The other parts are the same as those in FIG. 1, and thus will be described with reference to FIG.

Although the file system management unit 2a does not output a block discard request, for example, in the case of the FAT file system, the block detection mechanism 6 monitors the FAT to discard blocks with unnecessary marks. , And may notify the block device (including the conversion layer) of a “block discard request” for the detected block.

In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0033]

As described above, according to the present invention, when an unnecessary block exists on the file system, the address space of the EEPROM corresponding to the adjacent block is determined based on the unnecessary block. By making a request to discard or rewrite
An address space that does not require a ROM can be positively created, and the effective use of the EEPROM address space can be achieved.

Further, page erasing can be performed at a time while the address space of the EEPROM is increased, and the number of times of erasing can be reduced.

Further, since the erasing time of the EEPROM is longer than that of a normal device, the life of the EEPROM can be extended and the average writing speed can be increased by reducing the number of times of erasing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a file system according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the file system according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... User 2, 2a ... File system management part 3 ... Block address conversion layer 4 ... EEPROM 5 ... Management area 6 ... Block detection mechanism

Claims (4)

[Claims] 1. A file system in which a page erase type EEPROM is divided into a plurality of blocks and used as a block device, a relationship between a user request file and the blocks is defined, and a corresponding block is detected when a user request is received. And a correspondence relationship between the block and the address of the EEPROM, etc. is defined, a block requested by the user from the file system management unit is detected, and the EEPROM of the EEPROM corresponding to the detected block is detected. A block address conversion means for notifying a request content based on an address and performing processing according to the request content to the detection block; and a management area in a part of the plurality of divided blocks or an area other than these blocks. Is formed in the request notified from the conversion means. A file system comprising: the EEPROM for recording contents in the management area. 2. A file system which divides a page erasure type EEPROM into a plurality of blocks and uses the block device as a block device, wherein a file system management unit for transferring data between a user request and the block device; A relationship between the block and the block is defined, a block detection mechanism that detects a corresponding block when a user request is received and outputs a request, and a relationship between the block and an EEPROM address and the like is defined. Detecting a block requested by a user and the EEP corresponding to the detected block;
A block address conversion means for notifying the request content based on the address of the ROM and performing processing according to the request content to the detected block; and managing a part of the plurality of divided blocks or an area other than these blocks. A file system, comprising: an area in which an area is formed; and the EEPROM which records request contents notified from the conversion means in the management area. 3. When the content of the user request is a block discard request, the block / address conversion means detects the discard request block, stops holding unnecessary blocks, and informs the user that the block has been discarded. EEPR
3. The file system according to claim 1, wherein the OM is notified, and the EEPROM records an unnecessary mark in a corresponding area of the management area. 4. The content of a user request is a request for discarding or rewriting a block adjacent to an unnecessary mark added in the management area, thereby achieving an EEPR.
The file system according to any one of claims 1 to 3, wherein a space in the address space of the OM is increased to enable page erasure of the EEPROM.