Nachos试验10设计并实现具有二级索引的文件系统文档良心出品

1、实验目的最大能存取 NumDirect * SectorSize 的大小的文件,本次试Nachos系统原有的文件系统只支持单级索引, 验的目的： 理解文件系统的组织结构 扩展原有的文件系统,设计并实现具有二级索引的文件系统.实验环境linux操作系统,Nachos操作系统实验分析在文件头的定义中描述了：#define NumDirect (SectorSize - 2 * sizeof(int) / sizeof(int) 为了说明方便,经过实际计算,NumDirect = 30.二级索引的文件系统的filehdr首先,通过观察 Nachos原有的filehdr (即上图左边的局部),可知 N

2、achos的单级索引的文件系统最大 只支持存取29个扇区大小的文件.为了扩展二级索引,取数组的最后一个dataSectors29作为存取新的dataSectors 数组块的索弓I,定义 dataSectors0 - dataSectors28存取数据所在的块号,dataSectors29=-1表示无二级索引块,为正值表示二级索引dataSectors2所在的索引块.当文件超过原dataSectors数组所能能够存取的大小 28的时候,通过bitmap为文件头的dataSectors2分配空间,返回的 Sector号 存在 dataSectors29中.fileSys每次读取filehdr的时候

3、,仍然只读取原filehdr,如果想要访问和修改dataSectors2中的内容,那么在filehdr中先通过dataSectors29获取到dataSectors2 的扇区号,通过调用synchDisk ->ReadSector(dataSectorslastIndex, (char *)dataSectors2) ,读入 dataSectors2 的内容,然后再进行 dataSectors数组29-62号所对应的数据块的读取.由于本次实验是在实验 5的根底上进行更改的,即支持文件的扩展,这就要求不仅要有读取dataSectors2数组的方法,还要可以重新写入dataSectors2的

4、方法.实现方法也就是首先如果需要访问dataSectors2 ,那么首先调用 synchDisk -> ReadSector (dataSectorslastIndex, (char *)dataSectors2) ,读入 dataSectors2的内容,然后进行各种应用程序的读写操作,最后调用synchDisk -> WriteSector(dataSectorslastIndex, (char *)dataSectors2) ,将更改后的结果写回.由分析可知,文件系统的二级索引功能的扩展只针对filehdr ,所有的修改的都只在filehdr.cc中进行,连头文件filehdr

5、.h也不涉及.关键源代码及注释filehdr.cc在头文件中添加 dataSectors2 的大小定义：#define NumDirect2 (SectorSize / sizeof(int)更改 MaxFileSize :#define MaxFileSize (NumDirect + NumDirect2)* SectorSize)转向filehdr.cc进行说明,所有函数体中绿色局部均为本次实验的注释(建议看Allocate和Deallocate就好了,其他的原理类似,appSectors涉及实验5的局部)：/ filehdr.cc省略无数责任声明/ 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 dataSect

10、ors /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();dat

11、aSectorslastIndex = -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;

12、 i < 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

13、);return TRUE;AppSectors/FileHeader:AppSectors/LiZhen 10/31/2021/ 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 *fr

14、eeMap, 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;

15、elseint 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(mor

16、eFileSize, 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 n

17、eed the 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 allocat

18、e a new sector to stroe/the Secondary index block - dataSectors2./At last, write back the secondary index block into the sector.else(for( ; i< lastindex ; i+)dataSectorsi= freeMap ->Find();dataSectorslastindex = freeMap ->Find();int dataSectors2NumDirect2;for ( ; i < numSectors ; i+)data

19、Sectors2i - 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

20、sector,else(int dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastindex, (char *)dataSectors2);for( ; i < numSectors; i+)dataSectors2i-lastindex = freeMap -> Find();synchDisk->WriteSector(dataSectorslastindex, (char *)dataSectors2);)return TRUE;)Deallocate/ FileHeader:Deallocat

21、e/ De-allocate 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

22、 as original.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 t

23、his file./ At 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 *)dataSec

24、tors2);freeMap->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 (

25、the/ offset in 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) (

26、int lastindex = NumDirect - 1;if(offset / SectorSize < lastindex)return(dataSectorsoffset / SectorSize);else(int dataSectors2NumDirect2;synchDisk->ReadSector(dataSectorslastIndex, (char *)dataSectors2);return (dataSectors2offset / SectorSize - lastIndex);Print/ FileHeader:Print/ Print the cont

27、ents of the file 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 secondar

28、y index,/ handle it 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-

29、>ReadSector(dataSectorsi, 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 t

30、here is a secondary 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("FileHead

31、er contents. File size: %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->Re

32、adSector(dataSectorsi, 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); for( ; i < numSectors; i+) synchDis

33、k->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("n&qu

34、ot;);)delete data;)没有进行任何更改的函数void FileHeader:FetchFrom(int sector)void FileHeader:WriteBack(int sector) int FileHeader:FileLength()调试记录编译好Nachos之后,在终端敲入一下命令：studentlocalhost lab10$ ./nachos D得到运行结果(请一扫而过)：Bit map file header:FileHeader contents. File size: 128. File blocks:2File contents:0000000000

35、000000000Directory file header:FileHeader contents. File size: 200. File blocks: 3 4File contents:00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000Bi

36、tmap 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, s

37、ent 0Cleaning up.然后在终端中敲入如下代码,将 big文件复制到Nachos中：studentlocalhost lab10$ ./nachos -cp test/big big并执行append命令13次左右：studentlocalhost lab10$ ./nachos -ap test/big big最后显示结果关键局部加粗显示,其余局部一扫而过：studentlocalhost lab10$ ./nachos -DBit map file header:FileHeader contents. File size: 128. File blocks:2File con

38、tents: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, 24

39、, 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 abig