mkfs-simplefs.c

#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "simple.h"

#define WELCOMEFILE_DATABLOCK_NUMBER (SIMPLEFS_LAST_RESERVED_BLOCK + 1)
#define WELCOMEFILE_INODE_NUMBER (SIMPLEFS_LAST_RESERVED_INODE + 1)

static int write_superblock(int fd)
{
    struct simplefs_super_block sb = {
        .version = 1,
        .magic = SIMPLEFS_MAGIC,
        .block_size = SIMPLEFS_DEFAULT_BLOCK_SIZE,
        .inodes_count = WELCOMEFILE_INODE_NUMBER,
        /* FIXME: Free blocks management is not implemented yet */
        .free_blocks = (~0) & ~(1 << SIMPLEFS_LAST_RESERVED_BLOCK),
    };
    ssize_t ret;

    ret = write(fd, &sb, sizeof(sb));
    if (ret != SIMPLEFS_DEFAULT_BLOCK_SIZE) {
        printf
            ("bytes written [%d] are not equal to the default block size\n",
             (int)ret);
        return -1;
    }

    printf("Super block written succesfully\n");
    return 0;
}

static int write_root_inode(int fd)
{
    ssize_t ret;

    struct simplefs_inode root_inode;

    root_inode.mode = S_IFDIR;
    root_inode.inode_no = SIMPLEFS_ROOTDIR_INODE_NUMBER;
    root_inode.data_block_number = SIMPLEFS_ROOTDIR_DATABLOCK_NUMBER;
    root_inode.dir_children_count = 1;

    ret = write(fd, &root_inode, sizeof(root_inode));

    if (ret != sizeof(root_inode)) {
        printf
            ("The inode store was not written properly. Retry your mkfs\n");
        return -1;
    }

    printf("root directory inode written succesfully\n");
    return 0;
}
static int write_journal_inode(int fd)
{
    ssize_t ret;

    struct simplefs_inode journal;

    journal.inode_no = SIMPLEFS_JOURNAL_INODE_NUMBER;
    journal.data_block_number = SIMPLEFS_JOURNAL_BLOCK_NUMBER;

    ret = write(fd, &journal, sizeof(journal));

    if (ret != sizeof(journal)) {
        printf("Error while writing journal inode. Retry your mkfs\n");
        return -1;
    }

    printf("journal inode written succesfully\n");
    return 0;
}
static int write_welcome_inode(int fd, const struct simplefs_inode *i)
{
    off_t nbytes;
    ssize_t ret;

    ret = write(fd, i, sizeof(*i));
    if (ret != sizeof(*i)) {
        printf
            ("The welcomefile inode was not written properly. Retry your mkfs\n");
        return -1;
    }
    printf("welcomefile inode written succesfully\n");

    nbytes = SIMPLEFS_DEFAULT_BLOCK_SIZE - (sizeof(*i) * 3);
    ret = lseek(fd, nbytes, SEEK_CUR);
    if (ret == (off_t)-1) {
        printf
            ("The padding bytes are not written properly. Retry your mkfs\n");
        return -1;
    }

    printf
        ("inode store padding bytes (after the three inodes) written sucessfully\n");
    return 0;
}

int write_journal(int fd)
{
    ssize_t ret;
    ret = lseek(fd, SIMPLEFS_DEFAULT_BLOCK_SIZE * SIMPLEFS_JOURNAL_BLOCKS, SEEK_CUR);
    if (ret == (off_t)-1) {
        printf("Can't write journal. Retry you mkfs\n");
        return -1;
    }

    printf("Journal written successfully\n");
    return 0;
}

int write_dirent(int fd, const struct simplefs_dir_record *record)
{
    ssize_t nbytes = sizeof(*record), ret;

    ret = write(fd, record, nbytes);
    if (ret != nbytes) {
        printf
            ("Writing the rootdirectory datablock (name+inode_no pair for welcomefile) has failed\n");
        return -1;
    }
    printf
        ("root directory datablocks (name+inode_no pair for welcomefile) written succesfully\n");

    nbytes = SIMPLEFS_DEFAULT_BLOCK_SIZE - sizeof(*record);
    ret = lseek(fd, nbytes, SEEK_CUR);
    if (ret == (off_t)-1) {
        printf
            ("Writing the padding for rootdirectory children datablock has failed\n");
        return -1;
    }
    printf
        ("padding after the rootdirectory children written succesfully\n");
    return 0;
}
int write_block(int fd, char *block, size_t len)
{
    ssize_t ret;

    ret = write(fd, block, len);
    if (ret != len) {
        printf("Writing file body has failed\n");
        return -1;
    }
    printf("block has been written succesfully\n");
    return 0;
}

int main(int argc, char *argv[])
{
    int fd;
    ssize_t ret;

    char welcomefile_body[] = "Love is God. God is Love. Anbe Murugan.\n";
    struct simplefs_inode welcome = {
        .mode = S_IFREG,
        .inode_no = WELCOMEFILE_INODE_NUMBER,
        .data_block_number = WELCOMEFILE_DATABLOCK_NUMBER,
        .file_size = sizeof(welcomefile_body),
    };
    struct simplefs_dir_record record = {
        .filename = "vanakkam",
        .inode_no = WELCOMEFILE_INODE_NUMBER,
    };

    if (argc != 2) {
        printf("Usage: mkfs-simplefs <device>\n");
        return -1;
    }

    fd = open(argv[1], O_RDWR);
    if (fd == -1) {
        perror("Error opening the device");
        return -1;
    }

    ret = 1;
    do {
        if (write_superblock(fd))
            break;

        if (write_root_inode(fd))
            break;
        if (write_journal_inode(fd))
            break;
        if (write_welcome_inode(fd, &welcome))
            break;

        if (write_journal(fd))
            break;

        if (write_dirent(fd, &record))
            break;
        if (write_block(fd, welcomefile_body, welcome.file_size))
            break;

        ret = 0;
    } while (0);

    close(fd);
    return ret;
}