File Systems Exercise 3 Solution

Introduction




This exercise follows on from Tutorial Exercise 8. If you wait until the deadline to do this exercise it is unlikely that you will be able to finish the assignment 4.




You may work in pairs for this exercise, with your A4 partner, since some code will potentially be common with the assignment. MarkUs will only create the appropriate directory in your repository when you log into MarkUs and either create your group, or declare that you will work alone. The groups will get a new shared repository, and the students working solo may also get a new repository. Please log into MarkUs well before the deadline to take these steps. (If you create the directory in your repo yourself, then MarkUs won't know about it and we won't be able to see your work.)




It is your responsibility to log into MarkUs before the exercise deadline to ensure that you know where to commit your work, and so that MarkUs can connect your work to the grading system.




Requirements




Your final task in this series of exercises is to print the directory block contents. While you are doing this, you should work out how the directory structure creates a linked list of directory entries by using rec_len to show where the next directory entry begins. Note that rec_len in the last directory entry takes you to the end of the block.




When printing the blocks, first print the root directory. Then for each inode that is in use, check if it is a directory. If it is a directory, print the contents of the directory block. You do not need to print anything for file blocks.




For emptydisk.img your output should exactly match the following. In other words, we should be able to use diff to compare your output to this and see that it is identical (the indentation below uses 4 spaces).




Inodes: 32




Blocks: 128




Block group:




block bitmap: 3




inode bitmap: 4

inode table: 5




free blocks: 105




free inodes: 21




used_dirs: 2




Block bitmap: 11111111 11111111 11111100 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000001




Inode bitmap: 11111111 11100000 00000000 00000000




Inodes:




type: d size: 1024 links: 3 blocks: 2



Blocks: 9



Directory Blocks:




DIR BLOCK NUM: 9 (for inode 2)




Inode: 2 rec_len: 12 name_len: 1 type= d name=.




Inode: 2 rec_len: 12 name_len: 2 type= d name=..




Inode: 11 rec_len: 1000 name_len: 10 type= d name=lost+found




Note: The original twolevel.img was a bit confusing, so we uploaded a multilevel.img to the images directory and changed the output below.




For multilevel.img your output should match the following:




Inodes: 32




Blocks: 128




Block group:




block bitmap: 3




inode bitmap: 4




inode table: 5




free blocks: 102




free inodes: 17




used_dirs: 4




Block bitmap: 11111111 11111111 11111111 00000000 10000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000001




Inode bitmap: 11111111 11111110 00000000 00000000




Inodes:




type: d size: 1024 links: 4 blocks: 2



Blocks: 9



type: d size: 1024 links: 3 blocks: 2



Blocks: 23



type: d size: 1024 links: 2 blocks: 2



Blocks: 24



type: f size: 0 links: 1 blocks: 0



Blocks:



type: f size: 39 links: 1 blocks: 2
[15] Blocks:
33










Directory Blocks:
9 (for inode
2)




DIR
BLOCK
NUM:
type= d name=.


Inode:
2
rec_len:
12
name_len:
1


Inode:
2
rec_len:
12
name_len:
2
type= d name=..


Inode:
11
rec_len: 20 name_len:
10 type= d name=lost+found
Inode:
12
rec_len: 36 name_len:
6
type= d name=level1
Inode:
15
rec_len: 944 name_len: 5 type= f name=afile
DIR
BLOCK NUM: 23 (for inode
12)
Inode:
12
rec_len: 12
name_len:
1
type= d name=.
Inode:
2 rec_len: 12 name_len: 2 type= d name=..
Inode:
13
rec_len: 1000 name_len:
6 type= d name=level2
DIR
BLOCK NUM: 24 (for inode
13)
Inode:
13
rec_len: 12
name_len:
1
type= d name=.
Inode:
12
rec_len: 12
name_len:
2
type= d name=..
Inode:
14
rec_len: 1000 name_len:
5 type= f name=bfile
For largefile.img your output should match the following:




Inodes: 32




Blocks: 128




Block group:




block bitmap: 3




inode bitmap: 4




inode table: 5




free blocks: 90




free inodes: 20




used_dirs: 2




Block bitmap: 11111111 11111111 11111100 00000000 00010000 00000000 00000000 00000111 00000010 00000000 00111111 11110000 00000000 00000000 00000000 00000001




Inode bitmap: 11111111 11110000 00000000 00000000




Inodes:




type: d size: 1024 links: 3 blocks: 2



Blocks: 9



type: f size: 13440 links: 1 blocks: 30



Blocks: 62 63 64 83 84 85 86 87 88 89 90 91 36 0 0



Directory Blocks:




DIR BLOCK NUM: 9 (for inode 2)




Inode: 2 rec_len: 12 name_len: 1 type= d name=.




Inode: 2 rec_len: 12 name_len: 2 type= d name=..




Inode: 11 rec_len: 20 name_len: 10 type= d name=lost+found Inode: 12 rec_len: 980 name_len: 13 type= f name=largefile.txt Note that block list above for the file prints only the contents of the blocks array. An alternative approach would be to print the indices of the data blocks for the file: 62 63 64 83 84 85

86 87 88 89 90 91 92 71




Submission




Ensure that you have a repository directory created by MarkUs for this exercise (fs3), then add and commit readimage.c and ext2.h to this directory.