xv6/mkfs.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <assert.h>
#include "types.h"
#include "param.h"
#include "fs.h"

int nblocks = 1009;
int ninodes = 100;

int fsfd;
struct superblock sb;
char zeroes[512];
uint freeblock;
uint freeinode = 1;

void wsect(uint, void *);
void winode(uint, struct dinode *);
void rsect(uint sec, void *buf);
uint ialloc(ushort type);
void iappend(uint inum, void *p, int n);

// convert to intel byte order
ushort
xshort(ushort x)
{
  ushort y;
  uchar *a = (uchar *) &y;
  a[0] = x;
  a[1] = x >> 8;
  return y;
}

uint
xint(uint x)
{
  uint y;
  uchar *a = (uchar *) &y;
  a[0] = x;
  a[1] = x >> 8;
  a[2] = x >> 16;
  a[3] = x >> 24;
  return y;
}

main(int argc, char *argv[])
{
  int i, cc, fd;
  uint bn, rootino, inum;
  struct dirent de;
  char buf[512];

  if(argc < 2){
    fprintf(stderr, "Usage: mkfs fs.img files...\n");
    exit(1);
  }

  assert((512 % sizeof(struct dinode)) == 0);
  assert((512 % sizeof(struct dirent)) == 0);

  fsfd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
  if(fsfd < 0){
    perror(argv[1]);
    exit(1);
  }

  sb.nblocks = xint(nblocks); // so whole disk is 1024 sectors
  sb.ninodes = xint(ninodes);

  freeblock = ninodes / IPB + 2;

  for(i = 0; i < nblocks + (ninodes / IPB) + 3; i++)
    wsect(i, zeroes);

  wsect(1, &sb);

  rootino = ialloc(T_DIR);
  assert(rootino == 1);

  bzero(&de, sizeof(de));
  de.inum = xshort(rootino);
  strcpy(de.name, ".");
  iappend(rootino, &de, sizeof(de));

  bzero(&de, sizeof(de));
  de.inum = xshort(rootino);
  strcpy(de.name, "..");
  iappend(rootino, &de, sizeof(de));

  for(i = 2; i < argc; i++){
    assert(index(argv[i], '/') == 0);
    if((fd = open(argv[i], 0)) < 0){
      perror(argv[i]);
      exit(1);
    }

    inum = ialloc(T_FILE);

    bzero(&de, sizeof(de));
    de.inum = xshort(inum);
    strncpy(de.name, argv[i], DIRSIZ);
    iappend(rootino, &de, sizeof(de));
    
    while((cc = read(fd, buf, sizeof(buf))) > 0)
      iappend(inum, buf, cc);

    close(fd);
  }

  exit(0);
}

void
wsect(uint sec, void *buf)
{
  if(lseek(fsfd, sec * 512L, 0) != sec * 512L){
    perror("lseek");
    exit(1);
  }
  if(write(fsfd, buf, 512) != 512){
    perror("write");
    exit(1);
  }
}

uint
i2b(uint inum)
{
  return (inum / IPB) + 2;
}

void
winode(uint inum, struct dinode *ip)
{
  char buf[512];
  uint bn;
  struct dinode *dip;

  bn = i2b(inum);
  rsect(bn, buf);
  dip = ((struct dinode *) buf) + (inum % IPB);
  *dip = *ip;
  wsect(bn, buf);
}

void
rinode(uint inum, struct dinode *ip)
{
  char buf[512];
  uint bn;
  struct dinode *dip;

  bn = i2b(inum);
  rsect(bn, buf);
  dip = ((struct dinode *) buf) + (inum % IPB);
  *ip = *dip;
}

void
rsect(uint sec, void *buf)
{
  if(lseek(fsfd, sec * 512L, 0) != sec * 512L){
    perror("lseek");
    exit(1);
  }
  if(read(fsfd, buf, 512) != 512){
    perror("read");
    exit(1);
  }
}

uint
ialloc(ushort type)
{
  uint inum = freeinode++;
  struct dinode din;

  bzero(&din, sizeof(din));
  din.type = xshort(type);
  din.nlink = xshort(1);
  din.size = xint(0);
  winode(inum, &din);
  return inum;
}

#define min(a, b) ((a) < (b) ? (a) : (b))

void
iappend(uint inum, void *xp, int n)
{
  char *p = (char *) xp;
  uint fbn, off, n1;
  struct dinode din;
  char buf[512];

  rinode(inum, &din);

  off = xint(din.size);
  while(n > 0){
    fbn = off / 512;
    assert(fbn < NDIRECT);
    if(din.addrs[fbn] == 0)
      din.addrs[fbn] = xint(freeblock++);
    n1 = min(n, (fbn + 1) * 512 - off);
    rsect(xint(din.addrs[fbn]), buf);
    bcopy(p, buf + off - (fbn * 512), n1);
    wsect(xint(din.addrs[fbn]), buf);
    n -= n1;
    off += n1;
    p += n1;
  }
  din.size = xint(off);
  winode(inum, &din);
}