CN108763371A - A kind of Exfat file system power-off protection and file detect restoration methods - Google Patents
A kind of Exfat file system power-off protection and file detect restoration methods Download PDFInfo
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- CN108763371A CN108763371A CN201810475518.9A CN201810475518A CN108763371A CN 108763371 A CN108763371 A CN 108763371A CN 201810475518 A CN201810475518 A CN 201810475518A CN 108763371 A CN108763371 A CN 108763371A
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/14—Error detection or correction of the data by redundancy in operation
- G06F11/1402—Saving, restoring, recovering or retrying
- G06F11/1446—Point-in-time backing up or restoration of persistent data
- G06F11/1458—Management of the backup or restore process
Abstract
The present invention provides a kind of Exfat file system power-off protections and file to detect restoration methods, including：Determination will carry out the file directory item of write operation；Data are written into the data field of file；It is unfinished that mode of operation, which is arranged,；It is other values to change this document attribute directory item or the type feature value of stream extension directory entry or file-name extension directory entry any one；The value of 1 file size of file size, 2 field in update stream extension directory entry successively；Update corresponding cluster bitmap file and FAT table item；The verification of calculation document directory entry and, and the value update of sum will be verified in the checksum field in attribute directory item；Change back the value that step 4 is changed to original correctly value；It is to complete that mode of operation, which is arranged,.Meanwhile providing the restoration methods of corresponding document.The present invention solves the problems, such as that Exfat file system leads to file system corruption during write operation by accident power-off, and can realize the fast quick-recovery function of not writing file data.
Description
Technical field
The present invention relates to field of computer technology, especially in terms of file system storage, specifically, the present invention relates to
A kind of Exfat file system power-off protection and file detect restoration methods.
Background technology
In field of computer technology, it is related to a large amount of file storage work, needs to carry out write operation to file, if literary
Part system by accident power-off, then can cause part critical data in file system endless during to file write operation
It is whole, cause file system corruption, operating system that can not carry out normal operating to this document system.
Existing file system power-off protection method is to carry out double copies to data and daily record, or take and change to hardware
It makes, the method powered by backup power supply in accident power-off.It can reach file system power-off using the method for data backup to protect
The function of shield, but Backup Data can occupy disk space, and disk utilization is caused to reduce.Using the method for hardware modification,
It just cannot achieve under the environment that some hardware have been fixed.
Invention content
For deficiency present in existing file system cut-off guard method, the present invention provides a kind of Exfat files systems
Unite power-off protection and file detects restoration methods, can accident power-off causes file system during write operation to avoid file system
The problem of system damage, meanwhile, the file not operated when power is off can be restored.The present invention solves Exfat file system and exists
The problem of leading to file system corruption by accident power-off during write operation, and can realize the quick of the file data not write
Restore function.Technical scheme of the present invention is described as follows：
When carrying out write operation to Exfat file system, a very important item data is exactly file directory item.File directory
Xiang Yousan part forms, these three parts are referred to as attribute directory item, stream extension directory entry, file-name extension catalogue
?.The key message for including in attribute directory item has：The type feature value (0x85) of attribute directory item, attached catalogue item number, text
Part directory entry verifies and file attribute, file creation time, last modification time, last access time.In stream extension directory entry
Including key message have：The type feature value (0xC0) of stream extension directory entry, file fragmentation mark, filename number of characters, text
Part name hash value, file size 1, file size 2, starting cluster number.The key message for including in file-name extension directory entry has：Text
Part name extends the type feature value (0xC1) of directory entry, filename.
Exfat file system power-off protection method provided by the invention includes the following steps the write operation of file system：
1. the corresponding file directory item of file that determination will be operated records the initial address of this document directory entry.
2. the data of one section of designated length are written into the data field of this document.
3. it is unfinished that mode of operation, which is arranged,.
4. changing the type feature value of attribute directory item or stream extension directory entry or file-name extension directory entry any one
For other values.
5. the file size 1 in update stream extension directory entry, the value of 2 field of file size successively.
6. the corresponding cluster bitmap file of update and FAT table item.
7. the verification of calculation document directory entry and, and the value update of sum will be verified to the checksum field in attribute directory item
In.
8. changeing back the value that step 4 is changed to original correctly value.
9. it is to complete that mode of operation, which is arranged,.
10. step 2~9 are repeated, until operating writing-file terminates.
The mode of operation is stored in the reserved area of file system；The starting point of the corresponding file directory item of file of operation
Location is recorded in the reservation region of file system.
It after file system accident power-off re-powers, needs to be detected file system, detecting step includes：
1. the value of read operation state.
2. if mode of operation is to complete, file access pattern need not be carried out.
3. if the value of mode of operation is unfinished, illustrate the file for having operation unfinished when power-off.
4. reading the file directory item initial address of the file operated when power-off, file directory item information is obtained.
5. judging whether file directory item information is correct.
6. if this file directory item information is correct, illustrate that in just setting mode of operation be " unfinished ", also not to file
It is powered off when directory entry is modified, as long as mode of operation is revised as " completing ".
7. if this file directory item information is incorrect, illustrate when this corresponding file of file directory item is just powered off
The file of operation needs to restore this file.
File access pattern includes the following steps：
1. whether sentence file size 1 and the value of 2 field of file size in stream extension directory entry consistent.
2. if the value of 2 field of file size 1 and file size is inconsistent, the value of 1 field of file size is copied into text
2 field of part size continues following steps；If file size 1 is consistent with the value of 2 field of file size, continue directly to following
Step；
3. the verification of calculation document directory entry and, and the value update of sum will be verified to the checksum field in attribute directory item
In.
4. the characteristic value for the directory entry type changed is revised as correctly being worth.
5. mode of operation is revised as " completing ".
Beneficial effects of the present invention：Exfat file system power-off protection method provided by the invention need not carry out excessive
Data backup, so that it may with realize to file system power-off protection, and can quickly to power off before do not operate completion file progress
Restore, even if file can guarantee that the part having been written into can be read if a part is only written.
Description of the drawings
Fig. 1 is file system power-off protection file write operation flow chart of the present invention；
Fig. 2 is that accident power-off of the present invention re-powers file system overhaul flow chart；
Fig. 3 is file access pattern flow chart of the present invention.
Specific implementation mode
Below by specific implementation mode, the present invention is described in further detail：
In Windows operating system, for Exfat file system, if the attribute of the file directory item of some file
The type feature value that directory entry or stream extend any one of directory entry or file-name extension directory entry is incorrect, Windows systems
This would not be identified as a file by system, but still can carry out other operations to this document system.If this document mesh
It is all correct to record the attribute directory item in item, flow extension directory entry and the type feature value of file-name extension directory entry, and is flowed
Extend 2 field of 1 field of file size and file size in directory entry value is inconsistent or the verification of attribute directory item and not just
Really, file system is just damaged at this time, and Windows systems just can not carry out other operations to this document system.
Therefore, a kind of Exfat file system power-off protection method provided by the invention, is exactly utilized above-mentioned principle.
When carrying out operating writing-file to file system, it is first determined to carry out the file directory item of write operation file.If it is creating
A new file is built, first establishment file directory entry is needed, in establishment file directory entry, first by the attribute directory of file directory item
The type feature value of any one of item, stream extension directory entry, file-name extension directory entry is revised as other values.The present invention is with attribute
For directory entry, the type feature value of attribute directory item is set as 0x75, other fields of question paper directory entry all write as work(it
Afterwards, then by the type feature value of attribute directory item 0x85 is changed back.It is as follows：
1. the corresponding file directory item of file that determination will be operated, the initial address of this document directory entry is recorded in
In the reservation region of file system；
2. the data of one section of designated length are written into this document；
3. mode of operation is set as unfinished, mode of operation is stored in the reserved area of file system；
4. the type feature value of attribute directory item is changed to 0x75；
5. file size 1, the value of 2 field of file size in update stream extension directory entry；
6. the corresponding cluster bitmap file of update and FAT table item；
7. the verification of calculation document directory entry and, and the value update of sum will be verified to the checksum field in attribute directory item
In；
8. the type feature value for the attribute directory item changed in step 4 to be changed back to original value 0x85.
9. mode of operation is set as completing, mode of operation is stored in the reserved area of file system.
10. 2~9 steps are repeated, until file write operation terminates.
After file system accident power-off re-powers, it is necessary first to the file for whether having operation unfinished when detection power-off,
Detecting step includes：
1. read operation status information judges whether mode of operation is unfinished；
2. if mode of operation is to complete, file access pattern need not be carried out；
3. if mode of operation is unfinished, read the initial address of the operation file directory entry of record；
4. reading the file directory item letter for not completing operation file according to the initial address of the operation file directory entry of record
Breath, judges whether the directory entry of this document is complete；
5. if this file directory item information is correct, illustrate that in just setting mode of operation be " unfinished ", also not to file
It is powered off when directory entry is modified, as long as mode of operation is revised as " completing "；
6. if this file directory item information is incorrect, illustrate when this corresponding file of file directory item is just powered off
The file of operation needs to restore this file.
File recovery step is：
1. whether sentence file size 1 and the value of 2 field of file size in stream extension directory entry consistent；
2. if the value of 2 field of file size 1 and file size is inconsistent, the value of 1 field of file size is copied to
2 field of file size continues following steps；If file size 1 is consistent with the value of 2 field of file size, continue directly to
Lower step；
3. the verification of calculation document directory entry and, the type feature value of attribute directory item is by 0x85 progress when calculating, then
It will be in the value update to the checksum field of attribute directory item that sum be verified；
4. the type feature value for the attribute directory item changed is changed to correct value 0x85；
5. mode of operation is revised as " completing ".
Claims (3)
1. a kind of Exfat file system power-off protection method, which is characterized in that include the following steps：
1) determination will carry out the file directory item corresponding to the file of write operation, and the initial address of this document directory entry is recorded in
In the reservation region of file system；
2) data of one section of designated length are written into the data field of this document；
3) setting mode of operation is unfinished, and mode of operation is stored in the reserved area of file system；
4) this document attribute directory item, or the type spy of stream extension directory entry or file-name extension directory entry any one are changed
Value indicative is other values；
5) update stream extends file size 1, the value of 2 field of file size in directory entry successively；
6) corresponding cluster bitmap file and FAT table item are updated；
7) verification of calculation document directory entry and, and the value update of sum will be verified in the checksum field in attribute directory item；
8) value that step 4 is changed is changeed back to original correctly value；
9) setting mode of operation is to complete, and mode of operation is stored in the reserved area of file system；
10) step 2 is repeated to 9, until this document write operation is completed.
2. a kind of Exfat file system power-off protection file test method, which is characterized in that include the following steps：
1) value of read operation state；
2) if mode of operation is to complete, file access pattern need not be carried out；
If 3) value of mode of operation is unfinished, illustrate the file for having operation unfinished when power-off, continues following steps；
4) the file directory item initial address of the file operated when reading power-off obtains file directory item information；
5) judge whether file directory item information is correct；
If 6) this file directory item information is correct, illustrate that in just setting mode of operation be " unfinished ", also not to file directory
Item powers off when modifying, as long as mode of operation is revised as " completing "；
If 7) this file directory item information is incorrect, illustrate operating when this corresponding file of file directory item is just powered off
File, need to restore this file.
3. a kind of Exfat file system power-off protection file access pattern method, which is characterized in that include the following steps：
1) whether consistent sentence file size 1 and the value of 2 field of file size in stream extension directory entry；
If 2) value of 2 field of file size 1 and file size is inconsistent, the value of 1 field of file size is copied into file
2 field of size continues following steps；If file size 1 is consistent with the value of 2 field of file size, following step is continued directly to
Suddenly；
3) verification of calculation document directory entry and, and the value update of sum will be verified in the checksum field in attribute directory item；
4) characteristic value for the directory entry type changed is revised as correctly being worth；
5) mode of operation is revised as " completing ".
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