FileSystem

VFS using Fuse

To execute

$make
$./initialise

What is FUSE?

->VFS and FUSE are related, but not quite the same thing. The main purpose of FUSE is to turn things-that-are-almost-like-files-but-not-quite (such as files on a remote server, or inside a ZIP file) into "real" directories and files. See the roster of FUSE filesystems to get an idea of what this is good for; this hopefully will make it clearer why FUSE beats "plain old files" in a lot of circumstances.
->It provides a way to intercept file system calls issued by Linux programs and to redirect
the program flow into a handler (daemon running as a user-level process) function.
->It also helps to mount the file system.
->FUSE helps you in writing a virtual file system.

Workflow

main.c 
    functions start with fs_ 
    Intergrated with fuse (set fuse operations)
    Call syscall functions
syscall.c
    functions start with syscall_ 
    Do all Inode operations
    Call disk functions
disk.c
    functions start with disk_
    Do disk reads and writes

Files

disk.h -Disk emulator
disk.c -Disk emulator
syscall.c - System Calls
syscall.h - System Calls
initialise.c -Initialise disk and inodes
initialise.h -Initialise disk and inodes
log.txt - Log file
write_to_log.h - Writing to a log file
write_to_log.c - Writing to a log file

Functions in each file

"dir.c"
    -
    -
    -
"file.c"
    -
    -
    -
"disk.c"
    -int disk_init( const char *filename, int n ) 
        initialises the disk 
    -int disk_size()
        returns the number of blocks
    -static void sanity_check( int blocknum, const void *data )
        checks for the legality of the disk blocks
    -void disk_read(
     int blocknum, void*data )
        Disk read block by block
    -void disk_write( int blocknum, const void *data )
        Disk write block by block
    -void disk_close()
        closing the disk
    -void disk_attributes(){
        prints all the attributes like nblocks etc.

"initialise.c"
    -int init_superblock()
        creates superblock
    -int calculate_block_for_inode(int inodenumber)
        Given an inode number calculate block number
    -int calculate_offset_in_block(int inodenumber,int blocknum)
        Given inode number and blocknumber, calculate offset
    -initialise_free_block_bitmap()
        Set all datablocks to -1 in free_block_bitmap
    -int initialise_empty_inodes(int reset)
        Go through all inodes,Caculate block number and offset for them add it to i-list
    -void inode_atttributes_given_inodenumber(int inodenumber)
        print the attributes for that inode number
    -void inode_atttributes_given_inode(struct syscall_inode Inode)
        print the attributes for that inode 
    -void initialise_homeDir()
        Initialising a parent root directory (HOME)
    -int main()
        main driver function

"main.c"
    -static int fs_getattr(const char *path, struct stat *stbuf,struct fuse_file_info *fi)
        get attribute of a file fuse implementation.
    -static int fs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,off_t offset, struct fuse_file_info *fi) 
        read a directory using fuse
    -static int fs_open(const char *path, struct fuse_file_info *fi)
        open a file using fuse
    -static int fs_write(const char *path, const char *buf, size_t size,off_t offset, struct fuse_file_info *fi)
        write into a file using fuse
    -static int fs_read(const char *path, char *buf, size_t size, off_t offset,struct fuse_file_info *fi)
        read a file using fuse
    -static int fs_mkdir(const char *path, mode_t mode)
        make a directory using fuse
    -static int fs_rmdir(const char *path)
        remove a directory
    -static int utime(const char * path, struct utimbuf * timebuf)
        utime using fuse

"syscall.c"
    -int syscall_format(int reset)
        Creates a new filesystem on the disk, destroying any data already present
    -void syscall_debug()
        Report on how the inodes and blocks are organized
    -int syscall_mount()
        Examine the disk for a filesystem
    -int syscall_create_Inode()
        Create a new inode of zero length
    -int find_free_datablock()
        Find an available free datablock from free_block_bitmap
    -int syscall_initial_filetable()
        initialise all inode_numbers to -1.
    -int syscall_assign_filetable()
        check the first available filetable entry ,assign it and declare it's inode number
    -struct syscall_inode ReadInode(int inumber)
        Read specified inode from disk
    -int syscall_delete_Inode( int inumber )
        Delete the inode indicated by the inumber
    -int syscall_getsize( int inumber )
        Return the logical size of the given inode, in bytes
    -int syscall_find_next_free_file_descriptor()
        go through free_file_desc find next free one
    -int syscall_read( int inumber, char *data, int length, int offset )
        Read data from a valid inode
    -int syscall_write( int inumber, const char *data, int length, int offset )
        Write data to a valid inode