As a part of an exersice we are called to write a simple file system in C.
It will be a flat file system without directory hierarchy and without access control list.
These things must have:
Superblock (with information about the filesystem and the sizes of the below items)
Block bitmap (this can be done using ints, i dont know how to manipulate single bits)
i-node bitmap (same here)
Directory table (with high level filenames and the i-node indexes which have the info about the files)
i-nodes (This is the part were I'm stuck.)
I understand that an i-node indexes a group of blocks.
We cant store something smaller than the size of an i-node
(if its smaller the rest stays unoccupied if ts bigger we use more i-nodes)
- How many blocks per i-node do we assign?
(is it static or it depents from filesystem specs (num of blocks and block size)?)
- How do we point to a block of the disk in C?
(can we use pointers?)
I came up with these structures:
Any ideas if/how the above is going to work?Code:#define uint unsigned int
enum bool {false=0, true=1};
/* Block service structures */
struct superblock {
char fs_name[15];
uint sb_count; //number of blocks superblock occupies
uint block_size;
uint block_count; //number of blocks file system has
uint bbitmap_count; //number of blocks block bitmap occupies
uint free_blocks; //how many blocks are free
uint fs_rsv_blocks; //how many blocks are reserved from file system structs
uint inode_size; //how many block an inode indexes
uint inode_count; //total blocks occupied by inodes
uint ibitmap_count; //how many blocks occupied by inode bitmap
uint fs_rsv_inodes; //how many inodes reserved from file system structures
//i think its wrong the above but i grouped in inodes all the blocks of the disk so in some of
//them will hold filesystem's structures (will not be used at the end)
uint dir_table_count; //how many blocks the directory table occupies
};
//an array of them will be created depended on how many blocks the filesystem will be
struct block_bitmap {
enum bool block_bitmap;
};
/* File service structures */
//an array of them will be created depended on how many blocks the filesystem will be
struct inode_bitmap {
enum bool inode_bitmap;
};
//here i need help, an unsinged integer to point to the first block of the group (inode size will used to know how many blocks after it we have)
struct inode {
uint block;
};
//structure to hold a single file, file size is used to know, how many inodes we have to search
struct index {
uint file_size;
struct inode inode;
struct inode *indirect;
};
/* Directory service structures */
//a linked list will used to hold the filenames
struct dir_table {
char filename[16];
struct index index;
struct dir_table *next;
};
