ext2subs.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	clear_bit(b, eb.u.bmp);
	dirtyext2(eb);
	putext2(eb);
	
	es = getext2(xf, EXT2_SUPER, 0);
	es.u.sb->s_free_inodes_count++;
	dirtyext2(es); putext2(es);
}
int
create_dir(Xfile *fdir, char *name, int mode)
{
	Xfs *xf = fdir->xf;
	DirEntry *de;
	Inode *inode;
	Iobuf *buf, *ibuf;
	Xfile tf;
	int inr, baddr;

	inr = new_inode(fdir, mode);
	if( inr == 0 ){
		chat("create one new inode failed...");
		return -1;
	}
	if( add_entry(fdir, name, inr) < 0 ){
		chat("add entry failed...");
		free_inode(fdir->xf, inr);
		return -1;
	}

	/* create the empty dir */

	tf = *fdir;
	if( get_inode(&tf, inr) < 0 ){
		chat("can't get inode %d...", inr);
		free_inode(fdir->xf, inr);
		return -1;
	}

	ibuf = getbuf(xf, tf.bufaddr);
	if( !ibuf ){
		free_inode(fdir->xf, inr);
		return -1;
	}
	inode = ((Inode *)ibuf->iobuf) + tf.bufoffset;

	
	baddr = inode_getblk(&tf, 0);
	if( !baddr ){
		putbuf(ibuf);
		ibuf = getbuf(xf, fdir->bufaddr);
		if( !ibuf ){
			free_inode(fdir->xf, inr);
			return -1;
		}
		inode = ((Inode *)ibuf->iobuf) + fdir->bufoffset;
		delete_entry(fdir->xf, inode, inr);
		putbuf(ibuf);
		free_inode(fdir->xf, inr);
		return -1;
	}	
	
	inode->i_size = xf->block_size;	
	buf = getbuf(xf, baddr);
	
	de = (DirEntry *)buf->iobuf;
	de->inode = inr;
	de->name_len = 1;
	de->rec_len = DIR_REC_LEN(de->name_len);
	strcpy(de->name, ".");
	
	de = (DirEntry *)( (char *)de + de->rec_len);
	de->inode = fdir->inbr;
	de->name_len = 2;
	de->rec_len = xf->block_size - DIR_REC_LEN(1);
	strcpy(de->name, "..");
	
	dirtybuf(buf);
	putbuf(buf);
	
	inode->i_links_count = 2;
	dirtybuf(ibuf);
	putbuf(ibuf);
	
	ibuf = getbuf(xf, fdir->bufaddr);
	if( !ibuf )
		return -1;
	inode = ((Inode *)ibuf->iobuf) + fdir->bufoffset;

	inode->i_links_count++;

	dirtybuf(ibuf);
	putbuf(ibuf);

	return inr;
}
int
add_entry(Xfile *f, char *name, int inr)
{
	Xfs *xf = f->xf;
	DirEntry *de, *de1;
	int offset, baddr;
	int rec_len, cur_block;
	int namelen = strlen(name);
	Inode *inode;
	Iobuf *buf, *ibuf;

	ibuf = getbuf(xf, f->bufaddr);
	if( !ibuf )
		return -1;
	inode = ((Inode *)ibuf->iobuf) + f->bufoffset;

	if( inode->i_size == 0 ){
		chat("add_entry() no entry !!!...");
		putbuf(ibuf);
		return -1;
	}
	cur_block = offset = 0;
	rec_len = DIR_REC_LEN(namelen);
	buf = getbuf(xf, inode->i_block[cur_block++]);
	if( !buf ){
		putbuf(ibuf);
		return -1;
	}
	de = (DirEntry *)buf->iobuf;
	
	for(;;){
		if( ((char *)de) >= (xf->block_size + buf->iobuf) ){
			putbuf(buf);
			if( cur_block >= EXT2_NDIR_BLOCKS ){
				errno = Enospace;
				putbuf(ibuf);
				return -1;
			}
			if( (baddr = inode_getblk(f, cur_block++)) == 0 ){
				putbuf(ibuf);
				return -1;
			}
			buf = getbuf(xf, baddr);
			if( !buf ){
				putbuf(ibuf);
				return -1;
			}
			if( inode->i_size <= offset ){
				de  = (DirEntry *)buf->iobuf;
				de->inode = 0;
				de->rec_len = xf->block_size;
				dirtybuf(buf);
				inode->i_size = offset + xf->block_size;
				dirtybuf(ibuf);
			}else{
				de = (DirEntry *)buf->iobuf;
			}
		}
		if( de->inode != 0 && de->name_len == namelen &&
				!strncmp(name, de->name, namelen) ){
			errno = Eexist;
			putbuf(ibuf); putbuf(buf);
			return -1;
		}
		offset += de->rec_len;
		if( (de->inode == 0 && de->rec_len >= rec_len) ||
				(de->rec_len >= DIR_REC_LEN(de->name_len) + rec_len) ){
			if( de->inode ){
				de1 = (DirEntry *) ((char *)de + DIR_REC_LEN(de->name_len));
				de1->rec_len = de->rec_len - DIR_REC_LEN(de->name_len);
				de->rec_len = DIR_REC_LEN(de->name_len);
				de = de1;
			}	
			de->inode = inr;
			de->name_len = namelen;
			memcpy(de->name, name, namelen);
			dirtybuf(buf);
			putbuf(buf);
			inode->i_mtime = inode->i_ctime = time(0);
			dirtybuf(ibuf);
			putbuf(ibuf);
			return 0;
		}
		de = (DirEntry *)((char *)de + de->rec_len);
	}
	/* not reached */
}
int
unlink( Xfile *file )
{
	Xfs *xf = file->xf;	
	Inode *dir;
	int bg, b;
	Inode *inode;
	Iobuf *buf, *ibuf;
	Ext2 ed, es, eb;

	if( S_ISDIR(getmode(file)) && !empty_dir(file) ){
			chat("non empty directory...");
			errno = Eperm;
			return -1;
	}

	es = getext2(xf, EXT2_SUPER, 0);

	/* get dir inode */
	if( file->pinbr >= es.u.sb->s_inodes_count ){
    		chat("inode number %d is too big...",  file->pinbr);
		putext2(es);
		errno = Eintern;
    		return -1;
	}
	bg = (file->pinbr - 1) / xf->inodes_per_group;
	if( bg >= xf->ngroups ){
		chat("block group (%d) > groups count...", bg);
		putext2(es);
		errno = Eintern;
		return -1;
	}
	ed = getext2(xf, EXT2_DESC, bg);
	b = ed.u.gd->bg_inode_table +
			(((file->pinbr-1) % xf->inodes_per_group) / 
			xf->inodes_per_block);
	putext2(ed);
	buf = getbuf(xf, b);
	if( !buf ){	
		putext2(es);	
		return -1;
	}
	dir = ((struct Inode *) buf->iobuf) + 
		((file->pinbr-1) % xf->inodes_per_block);

	/* Clean dir entry */
	
	if( delete_entry(xf, dir, file->inbr) < 0 ){
		putbuf(buf);
		putext2(es);
		return -1;
	}
	if( S_ISDIR(getmode(file)) ){
		dir->i_links_count--;
		dirtybuf(buf);
	}
	putbuf(buf);
	
	/* clean blocks */
	ibuf = getbuf(xf, file->bufaddr);
	if( !ibuf ){
		putext2(es);
		return -1;
	}
	inode = ((Inode *)ibuf->iobuf) + file->bufoffset;

	if( !S_ISLNK(getmode(file)) || 
		(S_ISLNK(getmode(file)) && (inode->i_size > EXT2_N_BLOCKS<<2)) )
		if( free_block_inode(file) < 0 ){
			chat("error while freeing blocks...");
			putext2(es);
			putbuf(ibuf);
			return -1;
		}
	

	/* clean inode */	
	
	bg = (file->inbr -1) / xf->inodes_per_group;
	b = (file->inbr -1) % xf->inodes_per_group;

	eb = getext2(xf, EXT2_BINODE, bg);
	clear_bit(b, eb.u.bmp);
	dirtyext2(eb);
	putext2(eb);

	inode->i_dtime = time(0);
	inode->i_links_count--;
	if( S_ISDIR(getmode(file)) )
		inode->i_links_count = 0;

	es.u.sb->s_free_inodes_count++;
	dirtyext2(es);
	putext2(es);

	ed = getext2(xf, EXT2_DESC, bg);
	ed.u.gd->bg_free_inodes_count++;
	if( S_ISDIR(getmode(file)) )
		ed.u.gd->bg_used_dirs_count--;
	dirtyext2(ed);
	putext2(ed);

	dirtybuf(ibuf);
	putbuf(ibuf);

	return 1;
}
int
empty_dir(Xfile *dir)
{
	Xfs *xf = dir->xf;
	int nblock;
	uint offset, i,count;
	DirEntry *de;
	Inode *inode;
	Iobuf *buf, *ibuf;
	
	if( !S_ISDIR(getmode(dir)) )
		return 0;

	ibuf = getbuf(xf, dir->bufaddr);
	if( !ibuf )
		return -1;
	inode = ((Inode *)ibuf->iobuf) + dir->bufoffset;
	nblock = (inode->i_blocks * 512) / xf->block_size;

	for(i=0, count=0 ; (i < nblock) && (i < EXT2_NDIR_BLOCKS) ; i++){
		buf = getbuf(xf, inode->i_block[i]);
		if( !buf ){
			putbuf(ibuf);
			return 0;
		}
		for(offset=0 ; offset < xf->block_size ;  ){
			de = (DirEntry *)(buf->iobuf + offset);
			if(de->inode)
				count++;
			offset += de->rec_len;
		}
		putbuf(buf);
		if( count > 2 ){
			putbuf(ibuf);
			return 0;
		}
	}
	putbuf(ibuf);
	return 1;
}
int 
free_block_inode(Xfile *file)
{
	Xfs *xf = file->xf;
	int i, j, k;
	ulong b, *y, *z;
	uint *x;
	int naddr;
	Inode *inode;
	Iobuf *buf, *buf1, *buf2, *ibuf;

	ibuf = getbuf(xf, file->bufaddr);
	if( !ibuf )
		return -1;
	inode = ((Inode *)ibuf->iobuf) + file->bufoffset;

	for(i=0 ; i < EXT2_IND_BLOCK ; i++){
		x = inode->i_block + i;
		if( *x == 0 ){ putbuf(ibuf); return 0; }
		free_block(xf, *x);
	}
	naddr = xf->addr_per_block;

	/* indirect blocks */
	
	if( (b=inode->i_block[EXT2_IND_BLOCK]) ){
		buf = getbuf(xf, b);
		if( !buf ){ putbuf(ibuf); return -1; }
		for(i=0 ; i < naddr ; i++){
			x = ((uint *)buf->iobuf) + i;
			if( *x == 0 ) break;
			free_block(xf, *x);
		}
		free_block(xf, b);
		putbuf(buf);
	}

	/* double indirect block */

	if( (b=inode->i_block[EXT2_DIND_BLOCK]) ){
		buf = getbuf(xf, b);
		if( !buf ){ putbuf(ibuf); return -1; }
		for(i=0 ; i < naddr ; i++){
			x = ((uint *)buf->iobuf) + i;
			if( *x== 0 ) break;
			buf1 = getbuf(xf, *x);
			if( !buf1 ){ putbuf(buf); putbuf(ibuf); return -1; }
			for(j=0 ; j < naddr ; j++){
				y = ((ulong *)buf1->iobuf) + j;
				if( *y == 0 ) break;
				free_block(xf, *y);
			}
			free_block(xf, *x);
			putbuf(buf1);
		}
		free_block(xf, b);
		putbuf(buf);
	}
	
	/* triple indirect block */
	
	if( (b=inode->i_block[EXT2_TIND_BLOCK]) ){
		buf = getbuf(xf, b);
		if( !buf ){ putbuf(ibuf); return -1; }
		for(i=0 ; i < naddr ; i++){
			x = ((uint *)buf->iobuf) + i;
			if( *x == 0 ) break;
			buf1 = getbuf(xf, *x);
			if( !buf1 ){ putbuf(buf); putbuf(ibuf); return -1; }
			for(j=0 ; j < naddr ; j++){
				y = ((ulong *)buf1->iobuf) + j;
				if( *y == 0 ) break;
				buf2 = getbuf(xf, *y);
				if( !buf2 ){ putbuf(buf); putbuf(buf1); putbuf(ibuf); return -1; }
				for(k=0 ; k < naddr ; k++){
					z = ((ulong *)buf2->iobuf) + k;
					if( *z == 0 ) break;
					free_block(xf, *z);
				}
				free_block(xf, *y);
				putbuf(buf2);
			}
			free_block(xf, *x);
			putbuf(buf1);
		}
		free_block(xf, b);
		putbuf(buf);
	}

	putbuf(ibuf);
	return 0;
}
void free_block( Xfs *xf, ulong block )
{
	ulong bg;
	Ext2 ed, es, eb;

	es = getext2(xf, EXT2_SUPER, 0);

	bg = (block - es.u.sb->s_first_data_block) / xf->blocks_per_group;
	block = (block - es.u.sb->s_first_data_block) % xf->blocks_per_group;

	eb = getext2(xf, EXT2_BBLOCK, bg);
	clear_bit(block, eb.u.bmp);
	dirtyext2(eb);
	putext2(eb);

	es.u.sb->s_free_blocks_count++;
	dirtyext2(es);
	putext2(es);

	ed = getext2(xf, EXT2_DESC, bg);
	ed.u.gd->bg_free_blocks_count++;
	dirtyext2(ed);
	putext2(ed);

}
int 
delete_entry(Xfs *xf, Inode *inode, int inbr)
{
	int nblock = (inode->i_blocks * 512) / xf->block_size;
	uint offset, i;
	DirEntry *de, *pde;
	Iobuf *buf;
	
	if( !S_ISDIR(inode->i_mode) )
		return -1;

	for(i=0 ; (i < nblock) && (i < EXT2_NDIR_BLOCKS) ; i++){
		buf = getbuf(xf, inode->i_block[i]);
		if( !buf )
			return -1;
		pde = 0;
		for(offset=0 ; offset < xf->block_size ;  ){
			de = (DirEntry *)(buf->iobuf + offset);
			if( de->inode == inbr ){
				if( pde )
					pde->rec_len += de->rec_len;
				de->inode = 0;
				dirtybuf(buf);
				putbuf(buf);
				return 1;
			}
			offset += de->rec_len;
			pde = de;
		}
		putbuf(buf);

	}
	errno = Enonexist;
	return -1;
}
int
truncfile(Xfile *f)
{
	Inode *inode;
	Iobuf *ibuf;
	chat("trunc(fid=%d) ...", f->fid);
	ibuf = getbuf(f->xf, f->bufaddr);
	if( !ibuf )
		return -1;
	inode = ((Inode *)ibuf->iobuf) + f->bufoffset;
	
	if( free_block_inode(f) < 0 ){
		chat("error while freeing blocks...");
		putbuf(ibuf);
		return -1;
	}
	inode->i_atime = inode->i_mtime = time(0);
	inode->i_blocks = 0;
	inode->i_size = 0;
	memset(inode->i_block, 0, EXT2_N_BLOCKS*sizeof(ulong));
	dirtybuf(ibuf);
	putbuf(ibuf);
	chat("trunc ok...");
	return 0;
}
long
getmode(Xfile *f)
{
	Iobuf *ibuf;
	long mode;

	ibuf = getbuf(f->xf, f->bufaddr);
	if( !ibuf )
		return -1;
	mode = (((Inode *)ibuf->iobuf) + f->bufoffset)->i_mode;
	putbuf(ibuf);
	return mode;
}
void
CleanSuper(Xfs *xf)
{
	Ext2 es;

	es = getext2(xf, EXT2_SUPER, 0);
	es.u.sb->s_state = EXT2_VALID_FS;
	dirtyext2(es);
	putext2(es);
}
int 
test_bit(int i, void *data)
{
	char *pt = (char *)data;

	return pt[i>>3] & (0x01 << (i&7));
}

int
set_bit(int i, void *data)
{
  	char *pt;

  	if( test_bit(i, data) )
    		return 1; /* bit already set !!! */
  
  	pt = (char *)data;
  	pt[i>>3] |= (0x01 << (i&7));

  	return 0;
}

int 
clear_bit(int i, void *data)
{
	char *pt;

  	if( !test_bit(i, data) )
    		return 1; /* bit already clear !!! */
  
 	 pt = (char *)data;
  	pt[i>>3] &= ~(0x01 << (i&7));
	
	return 0;
}
void *
memscan( void *data, int c, int count )
{
	char *pt = (char *)data;

	while( count ){
		if( *pt == c )
			return (void *)pt;
		count--;
		pt++;
	}
	return (void *)pt;
}

int 
find_first_zero_bit( void *data, int count /* in byte */)
{
  char *pt = (char *)data;
  int n, i;
  
  n = 0;

  while( n < count ){
    for(i=0 ; i < 8 ; i++)
      if( !(*pt & (0x01 << (i&7))) )
	return (n<<3) + i;
    n++; pt++;
  }
  return n << 3;
}

int 
find_next_zero_bit( void *data, int count /* in byte */, int where)
{
  char *pt = (((char *)data) + (where >> 3));
  int n, i;
  
  n = where >> 3;
  i = where & 7;

  while( n < count ){
    for(; i < 8 ; i++)
      if( !(*pt & (0x01 << (i&7))) )
	return (n<<3) + i;
    n++; pt++; i=0;
  }
  return n << 3;
}
int
ffz( int x )
{
	int c = 0;
	while( x&1 ){
		c++;
		x >>= 1;
	}
	return c;
}