Directory Resolution

// linux/fs/open.c
int sys_open(const char* filename, int flag)
{  
	i=open_namei(filename,flag,&inode);
	// ... 
}

int open_namei(...)
{ 
	dir=dir_namei(pathname,&namelen,&basename);

static struct m_inode *dir_namei()
{  dir=get_dir(pathname); }

static struct m_inode *get_dir(const char *pathname)
{
	if((c=get_fs_byte(pathname))==‘/’){
		inode=current->root; 
		pathname++;
	}
	else if(c) inode=current->pwd; 
	while(1){ //函数的正确出口
		if(!c) return inode; 
		bh=find_entry(&inode,thisname,namelen,&de);
		int inr=de->inode;
		int idev=inode->i_dev;
		inode=iget(idev,inr); //根据目录项读取下一层inode
	}
	// ...
}

• root:找到根目录;

• find_entry:从目录中读取目录项;

• inr:是目录项中的索引节点号;

• iget:再读下一层目录

从根目录开始解析

void init(void) 
{ 
	setup((void *) &drive_info); 
	// ... 

// kernel/hd.c
sys_setup(void * BIOS)
{ 
	hd_info[drive].head = *(2+BIOS);
	hd_info[drive].sect = *(14+BIOS);
	mount_root(); 
	... 
}

// fs/super.c
void mount_root(void) 
{
   mi=iget(ROOT_DEV,ROOT_INO));
   current->root = mi;
}

读取inode

struct m_inode * iget(int dev, int nr)
{ 
	struct m_inode *inode = get_empty_inode();
	inode->i_dev=dev; inode->i_num=nr;
	read_inode(inode); return inode;
}

static void read_inode(struct m_inode *inode)
{
	struct super_block *sb=get_super(inode->i_dev);
	lock_inode(inode);
	block=2+sb->s_imap_blocks+sb->s_zmap_blocks+
        (inode->i_num-1)/INODES_PER_BLOCK;
	bh=bread(inode->i_dev,block); 
	inode=bh->data[(inode->i_num-1)%INODES_PER_BLOCK]; 
	unlock_inode(inode); 
}

开始目录解析

struct dir_entry
{
	unsigned short inode; //i节点号 
	char name[NAME_LEN]; //文件名 
}

// fs/namei.c
static struct buffer_head *find_entry(struct m_inode **dir, 
	char *name, ..., struct dir_entry ** res_dir)
{ 
	int entries=(*dir)->i_size/(sizeof(struct dir_entry));
	int block=(*dir)->i_zone[0];
	*bh=bread((*dir)->i_dev, block);
	struct dir_entry *de =bh->b_data;
	while(i<entries) { 
		if((char*)de>=BLOCK_SIZE+bh->b_data){
			brelse(bh);
			block=bmap(*dir,i/DIR_ENTRIES_PER_BLOCK);
			bh=bread((*dir)->i_dev,block);
			de=(struct dir_entry*)bh->b_data;
		} //读入下一块上的目录项继续match
		if(match(namelen,name,de)){
			*res_dir=de; 
			return bh;
		}
		de++; 
		i++;
	}
}