Nachos實驗10設計并實現(xiàn)具有二級索引的文件系統(tǒng)

1、實驗目的最大能存取 NumDirect * SectorSize 的大小的文件，本次試Nachos系統(tǒng)原有的文件系統(tǒng)只支持單級索引， 驗的目的： 理解文件系統(tǒng)的組織結構 擴展原有的文件系統(tǒng)，設計并實現(xiàn)具有二級索引的文件系統(tǒng)。實驗環(huán)境linux操作系統(tǒng)，Nachos操作系統(tǒng)實驗分析已知在文件頭的定義中描述了：#define NumDirect (SectorSize - 2 * sizeof(int) / sizeof(int) 為了說明方便，經過實際計算，NumDirect = 30.二級索引的文件系統(tǒng)的filehdr首先，通過觀察 Nachos原有的filehdr (即上圖左邊的部分)，可知

2、 Nachos的單級索引的文件系統(tǒng)最大 只支持存取29個扇區(qū)大小的文件。為了擴展二級索引，取數(shù)組的最后一個dataSectors29作為存取新的dataSectors 數(shù)組塊的索弓I,定義 dataSectors0 - dataSectors28存取數(shù)據(jù)所在的塊號，dataSectors29=-1表示無二級索引塊，為正值表示二級索引dataSectors2所在的索引塊。當文件超過原dataSectors數(shù)組所能能夠存取的大小 28的時候，通過bitmap為文件頭的dataSectors2分配空間，返回的 Sector號 存在 dataSectors29中。fileSys每次讀取filehdr的

3、時候，仍然只讀取原filehdr,如果想要訪問和修改dataSectors2中的內容，則在filehdr中先通過dataSectors29獲取到dataSectors2 的扇區(qū)號，通過調用synchDisk ->ReadSector(dataSectorslastIndex, (char *)dataSectors2) ,讀入 dataSectors2 的內容，然后再進行 dataSectors數(shù)組29-62號所對應的數(shù)據(jù)塊的讀取。因為本次實驗是在實驗 5的基礎上進行更改的，即支持文件的擴展，這就要求不僅要有讀取dataSectors2數(shù)組的方法，還要可以重新寫入dataSectors2

4、的方法。實現(xiàn)方法也就是首先如果需要訪問dataSectors2 ,那么首先調用 synchDisk -> ReadSector (dataSectorslastIndex, (char *)dataSectors2) ,讀入 dataSectors2的內容，然后進行各種應用程序的讀寫操作，最后調用synchDisk -> WriteSector(dataSectorslastIndex, (char *)dataSectors2) ,將更改后的結果寫回。由分析可知，文件系統(tǒng)的二級索引功能的擴展只針對filehdr,所有的修改的都只在filehdr.cc中進行，連頭文件filehdr

5、.h也不涉及。關鍵源代碼及注釋filehdr.cc在頭文件中添加 dataSectors2 的大小定義：#define NumDirect2 (SectorSize / sizeof(int)更改 MaxFileSize :#define MaxFileSize (NumDirect + NumDirect2)* SectorSize)轉向filehdr.cc進行說明，所有函數(shù)體中綠色部分均為本次實驗的注釋(建議看Allocate和Deallocate就好了，其他的原理類似，appSectors涉及實驗5的部分)：/ filehdr.cc省略無數(shù)責任聲明/ LiZhen 17/11/09/ E

6、xtends the file system to double the max file size that/ Nachos can store#include "copyright.h"#include "system.h"#include "filehdr.h"Allocate/ FileHeader:Allocate/ Initialize a fresh file header for a newly created file./ Allocate data blocks for the file out of the ma

7、p of free disk blocks./ Return FALSE if there are not enough free blocks to accomodate/ the new file./ "freeMap" is the bit map of free disk sectors/ "fileSize" is the bit map of free disk sectors/ LiZhen 17/11/09/ Extends the file system to double the max file size that / Nachos

8、 can store/ Current max file size of Nachos file system is/ (NumDirect + NumDirect2) * SectorSize/ If the dataSectorsNumDirect - 1 = -1, no secondary index./ otherwise, use the dataSecotrsNumDirect - 1 to stroe the/ pointer to the secondary index block - dataSectors2口./boolFileHeader:Allocate(BitMap

9、 *freeMap, int fileSize)numBytes = fileSize;numSectors = divRoundUp(fileSize, SectorSize);if (freeMap->NumClear() < numSectors)return FALSE; / not enough spaceelse if(NumDirect + NumDirect2 <= numSectors)return FALSE;not enough pointer space/First figure out the current length of dataSector

10、s /dataSectors array index ranges from 0 to lastIndex-1 int lastIndex=NumDirect-1;/If do not need the secondary index, /do not change the original code except /assign dataSectorslastIndex = -1 if(numSectors < lastindex)for (int i = 0; i < numSectors; i+)dataSectorsi = freeMap->Find();dataSe

11、ctorslastIndex = -1;/If the numSectors excends the rage of dataSectors, /first handle the first 0-lastIndex-1 as before./Then, ask bitmap to allocate a new sector to stroe /the Secondary index block - dataSectors2./At last, write back the secondary index block into the sector.elsefor (int i = 0; i &

12、lt; lastIndex; i+)dataSectorsi = freeMap->Find();dataSectorslastIndex = freeMap->Find();int dataSectors2NumDirect2;secondary index blockfor (int i = 0; i < numSectors - NumDirect; i+)dataSectors2i = freeMap->Find();synchDisk->WriteSector(dataSectorslastIndex, (char *)dataSectors2);ret

13、urn TRUE;AppSectors/FileHeader:AppSectors/LiZhen 10/31/2009 In lab5/ add appFileSize more bytes in the current file/ refresh the bitmap to show the allocating changes./LiZhen 17/11/09/ In lab10/ Handle the reading and writing of the dataSectors2/ if needed./boolFileHeader:AppSectors(BitMap *freeMap,

14、 int appFileSize) if(appFileSize <= 0)return false;int restFileSize = SectorSize * numSectors - numBytes;/ printf("the moreFileSize is %dn",moreFileSize);/ printf("the appFileSize is %dn",appFileSize);if(restFileSize >= appFileSize)numBytes += appFileSize;return true;elsein

15、t moreFileSize = appFileSize - restFileSize;if(freeMap->NumClear()< divRoundUp(moreFileSize, SectorSize)return FALSE;else if(NumDirect + NumDirect2 <= numSectors + divRoundUp(moreFileSize, SectorSize) return FALSE;int i = numSectors;numBytes += appFileSize;numSectors += divRoundUp(moreFileS

16、ize, SectorSize);/* In lab10*/First figure out the current length of dataSectors/dataSectors array index ranges from 0 to lastIndex-1int lastIndex = NumDirect-1;/* If before appending, there is no secondary index*/if(dataSectorslastIndex = -1)/If after being appended, new dataSecoters do NOT need th

17、e secondary index,/do not change the original code.if(numSectors < lastindex)for( ; i < numSectors; i+) dataSectorsi = freeMap -> Find();/If after being appended, new dataSecoters DO need the secondary index, /first handle the first 0-lastIndex-1 as before./Then, ask bitmap to allocate a ne

18、w sector to stroe/the Secondary index block - dataSectors2./At last, write back the secondary index block into the sector.elsefor( ; i< lastindex ; i+)dataSectorsi= freeMap ->Find();dataSectorslastIndex = freeMap ->Find();int dataSectors2NumDirect2;for ( ; i < numSectors ; i+)dataSectors

19、2i - lastindex = freeMap->Find();synchDisk->WriteSector(dataSectorslastIndex, (char *)dataSectors2);/* If before appending, there is already a secondary index*/First read the dataSectors2 from the Disk./Then, append the file size./At last, write back the secondary index block into the sector,e

20、lseint dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastIndex, (char *)dataSectors2);for( ; i < numSectors; i+)dataSectors2i-lastIndex = freeMap -> Find();synchDisk->WriteSector(dataSectorslastIndex, (char *)dataSectors2);return TRUE;Deallocate/ FileHeader:Deallocate/ De-alloc

21、ate all the space allocated for data blocks for this file./ "freeMap" is the bit map of free disk sectors/ LiZhen 17/11/09/ Deallocate the dataSectors2 if needed./voidFileHeader:Deallocate(BitMap *freeMap)int lastIndex = NumDirect - 1;/ If there is no secondary index,/ handle it as origina

22、l.if(dataSectorslastIndex=-1)for (int i = 0; i < numSectors; i+)ASSERT(freeMap->Test(int) dataSectorsi); / ought to be marked!freeMap->Clear(int) dataSectorsi);/ If there is a secondary index,/ first read in the dataSectors2 from the Disk./ Then, deallocate the data blocks for this file./ A

23、t last, deallocate the block that dataSector2 locates.elseint i=0;for ( ; i < lastindex; i+)ASSERT(freeMap->Test(int) dataSectorsi); / ought to be marked!freeMap->Clear(int) dataSectorsi);int dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastIndex, (char *)dataSectors2);freeMap

24、->Clear(int) dataSectorslastIndex);for( ; i < numSectors; i+)freeMap->Clear(int) dataSectors2i-lastIndex);ByteToSectors/ FileHeader:ByteToSector/ Return which disk sector is storing a particular byte within the file./ This is essentially a translation from a virtual address (the/ offset in

25、the file) to a physical address (the sector where the/ data at the offset is stored)./ "offset" is the location within the file of the byte in question / LiZhen 17/11/09/ Handle the reading and writing of the dataSectors2 / if needed./intFileHeader:ByteToSector(int offset) int lastindex =

26、NumDirect - 1;if(offset / SectorSize < lastindex)return(dataSectorsoffset / SectorSize);elseint dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastIndex, (char *)dataSectors2);return (dataSectors2offset / SectorSize - lastindex);Print/ FileHeader:Print/ Print the contents of the file

27、header, and the contents of all the data blocks pointed to by the file header./ LiZhen 17/11/09/ Handle the reading and writing of the dataSectors2/ if needed./voidFileHeader:Print()int i, j, k;int lastindex = NumDirect - 1;char *data = new charSectorSize;/ If there is no secondary index,/ handle it

28、 as original.if(dataSectorslastIndex = -1)printf("FileHeader contents. File size: %d. File blocks:n", numBytes);for (i = 0; i < numSectors; i+)printf("%d ", dataSectorsi);printf("nFile contents:n");for (i = k = 0; i < numSectors; i+) synchDisk->ReadSector(dataS

29、ectorsi, data);for (j = 0; (j < SectorSize) && (k < numBytes); j+, k+) if (''040' <= dataj && dataj <= '176')/ isprint(dataj)printf("%c", dataj);elseprintf("%x", (unsigned char)dataj);printf("n");/ If there is a secondary

30、index,/ first read in the dataSectors2 from the Disk./ Then, deallocate the data blocks for this file./ At last, deallocate the block that dataSector2 locates.elseint dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastIndex, (char *)dataSectors2);printf("FileHeader contents. File si

31、ze: %d. File blocks:n", numBytes);for (i = 0; i < lastIndex; i+)printf("%d ", dataSectorsi);for(; i < numSectors; i+)printf("%d ", dataSectors2i - lastIndex);printf("nFile contents:n");for (i = k = 0; i < lastIndex; i+) synchDisk->ReadSector(dataSectors

32、i, data);for (j = 0; (j < SectorSize) && (k < numBytes); j+, k+) if ('040' <= dataj && dataj <= '176')/ isprint(dataj)printf("%c", dataj);elseprintf("%x", (unsigned char)dataj);printf("n");for( ; i < numSectors; i+) synchDi

33、sk->ReadSector(dataSectors2i - lastindex, data);for (j = 0; (j < SectorSize) && (k < numBytes); j+, k+) if (''040' <= dataj && dataj <= '176')/ isprint(dataj)printf("%c", dataj);elseprintf("%x", (unsigned char)dataj);printf("

34、;n");delete data;沒有進行任何更改的函數(shù)void FileHeader:FetchFrom(int sector)void FileHeader:WriteBack(int sector) int FileHeader:FileLength()調試記錄編譯好Nachos之后，在終端敲入一下命令：studentlocalhost lab10$ ./nachos D得到運行結果(請一掃而過)：Bit map file header:FileHeader contents. File size: 128. File blocks:2File contents:0000000

35、000000000000Directory file header:FileHeader contents. File size: 200. File blocks: 3 4File contents:0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

36、0Bitmap set:0,1,2, 3, 4,Directory contents:No threads ready or runnable, and no pending interrupts.Assuming the program completed.Machine halting!Ticks: total 5400, idle 5060, system 340, user 0Disk I/O: reads 10, writes 0Console I/O: reads 0, writes 0Paging: faults 0Network I/O: packets received 0,

37、 sent 0Cleaning up.然后在終端中敲入如下代碼，將 big文件復制到Nachos中：studentlocalhost lab10$ ./nachos -cp test/big big并執(zhí)行append命令13次左右：studentlocalhost lab10$ ./nachos -ap test/big big最后顯示結果（關鍵部分加粗顯示，其余部分一掃而過）：studentlocalhost lab10$ ./nachos -DBit map file header:FileHeader contents. File size: 128. File blocks:2File

38、 contents:0000000000000000000Directory file header:FileHeader contents. File size: 200. File blocks:3 4File contents:00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000Bitmap set:0,1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,

39、 24, 25, 26, 27, 28, 29, 30,31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41,42, 43, 44,Directory contents:Name: big, Sector: 5FileHeader contents. File size: 4760. File blocks:6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 36 37 38 39 40 4142 43 44File contents:big file big file big file big file big file a