luminoid / simple-file-system

UCSB CS170: Project 5 - Simple File System

Simple File System

File System Structure

Super Block

Space: Block 0

typedef struct
{
    // Directory info
    int dir_index;
    int dir_len;

    // Data info
    int data_index;
} super_block;

Directory infomation

Space: Block 1 Function: List of file information.

typedef struct
{
    bool used;                   // whether the file is being used
    char name[MAX_FILENAME_LEN]; // file name
    int size;                    // file size
    int head;                    // first data block
    int num_blocks;              // number of blocks
    int fd_count;                // number of file descriptors using this file
} file_info;

Data block usage

Space: Block 2-3 Function: Store the file index of each block.

Data blocks

Space: Block 4-8191 Function: Store the data of the file.

Function Implementation

File system management

make_fs(char *disk_name)

1. Initialize the super block
2. Write the super block to disk

mount_fs(char *disk_name)

1. Read super block
2. Read directory info
3. Clear file descriptors

umount_fs(char *disk_name)

1. Write directory info
2. Clear file descriptors

File system operations

fs_open(char *name)

1. Allocate a file descriptor

fs_close(int fildes)

1. Free the allocated file descriptor

fs_create(char *name)

1. Initialize file information

fs_delete(char *name)

1. Remove file information
2. Free file blocks

fs_read(int fildes, void *buf, size_t nbyte)

1. Load current block
2. Read current block
3. Read the following blocks

fs_write(int fildes, void *buf, size_t nbyte)

1. Load current block
2. Write current block
3. Write the allocated blocks
4. Write into new blocks

fs_get_filesize(int fildes)

1. Get file info from the file descriptor table

fs_lseek(int fildes, off_t offset)

1. Modify fd of the file descriptor table

fs_truncate(int fildes, off_t length)

1. Free blocks
2. Modify file information
3. Truncate fd offset

Helper function

1. char find_file(char* name)
2. int find_free_file_des(char file_index)
3. int find_free_block(char file_index)
4. int find_next_block(int current, char file_index)