namei.c

来自「目前最为完备的早期Linux系统C源代码,版本为0.11,内有详细注释.」· C语言 代码 · 共 779 行 · 第 1/2 页

	}
	inr = de->inode;
	dev = dir->i_dev;
	brelse(bh);
	iput(dir);
	if (flag & O_EXCL)
		return -EEXIST;
	if (!(inode=iget(dev,inr)))
		return -EACCES;
	if ((S_ISDIR(inode->i_mode) && (flag & O_ACCMODE)) ||
	    !permission(inode,ACC_MODE(flag))) {
		iput(inode);
		return -EPERM;
	}
	inode->i_atime = CURRENT_TIME;
	if (flag & O_TRUNC)
		truncate(inode);
	*res_inode = inode;
	return 0;
}

int sys_mknod(const char * filename, int mode, int dev)
{
	const char * basename;
	int namelen;
	struct m_inode * dir, * inode;
	struct buffer_head * bh;
	struct dir_entry * de;
	
	if (!suser())
		return -EPERM;
	if (!(dir = dir_namei(filename,&namelen,&basename)))
		return -ENOENT;
	if (!namelen) {
		iput(dir);
		return -ENOENT;
	}
	if (!permission(dir,MAY_WRITE)) {
		iput(dir);
		return -EPERM;
	}
	bh = find_entry(&dir,basename,namelen,&de);
	if (bh) {
		brelse(bh);
		iput(dir);
		return -EEXIST;
	}
	inode = new_inode(dir->i_dev);
	if (!inode) {
		iput(dir);
		return -ENOSPC;
	}
	inode->i_mode = mode;
	if (S_ISBLK(mode) || S_ISCHR(mode))
		inode->i_zone[0] = dev;
	inode->i_mtime = inode->i_atime = CURRENT_TIME;
	inode->i_dirt = 1;
	bh = add_entry(dir,basename,namelen,&de);
	if (!bh) {
		iput(dir);
		inode->i_nlinks=0;
		iput(inode);
		return -ENOSPC;
	}
	de->inode = inode->i_num;
	bh->b_dirt = 1;
	iput(dir);
	iput(inode);
	brelse(bh);
	return 0;
}

int sys_mkdir(const char * pathname, int mode)
{
	const char * basename;
	int namelen;
	struct m_inode * dir, * inode;
	struct buffer_head * bh, *dir_block;
	struct dir_entry * de;

	if (!suser())
		return -EPERM;
	if (!(dir = dir_namei(pathname,&namelen,&basename)))
		return -ENOENT;
	if (!namelen) {
		iput(dir);
		return -ENOENT;
	}
	if (!permission(dir,MAY_WRITE)) {
		iput(dir);
		return -EPERM;
	}
	bh = find_entry(&dir,basename,namelen,&de);
	if (bh) {
		brelse(bh);
		iput(dir);
		return -EEXIST;
	}
	inode = new_inode(dir->i_dev);
	if (!inode) {
		iput(dir);
		return -ENOSPC;
	}
	inode->i_size = 32;
	inode->i_dirt = 1;
	inode->i_mtime = inode->i_atime = CURRENT_TIME;
	if (!(inode->i_zone[0]=new_block(inode->i_dev))) {
		iput(dir);
		inode->i_nlinks--;
		iput(inode);
		return -ENOSPC;
	}
	inode->i_dirt = 1;
	if (!(dir_block=bread(inode->i_dev,inode->i_zone[0]))) {
		iput(dir);
		free_block(inode->i_dev,inode->i_zone[0]);
		inode->i_nlinks--;
		iput(inode);
		return -ERROR;
	}
	de = (struct dir_entry *) dir_block->b_data;
	de->inode=inode->i_num;
	strcpy(de->name,".");
	de++;
	de->inode = dir->i_num;
	strcpy(de->name,"..");
	inode->i_nlinks = 2;
	dir_block->b_dirt = 1;
	brelse(dir_block);
	inode->i_mode = I_DIRECTORY | (mode & 0777 & ~current->umask);
	inode->i_dirt = 1;
	bh = add_entry(dir,basename,namelen,&de);
	if (!bh) {
		iput(dir);
		free_block(inode->i_dev,inode->i_zone[0]);
		inode->i_nlinks=0;
		iput(inode);
		return -ENOSPC;
	}
	de->inode = inode->i_num;
	bh->b_dirt = 1;
	dir->i_nlinks++;
	dir->i_dirt = 1;
	iput(dir);
	iput(inode);
	brelse(bh);
	return 0;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
static int empty_dir(struct m_inode * inode)
{
	int nr,block;
	int len;
	struct buffer_head * bh;
	struct dir_entry * de;

	len = inode->i_size / sizeof (struct dir_entry);
	if (len<2 || !inode->i_zone[0] ||
	    !(bh=bread(inode->i_dev,inode->i_zone[0]))) {
	    	printk("warning - bad directory on dev %04x\n",inode->i_dev);
		return 0;
	}
	de = (struct dir_entry *) bh->b_data;
	if (de[0].inode != inode->i_num || !de[1].inode || 
	    strcmp(".",de[0].name) || strcmp("..",de[1].name)) {
	    	printk("warning - bad directory on dev %04x\n",inode->i_dev);
		return 0;
	}
	nr = 2;
	de += 2;
	while (nr<len) {
		if ((void *) de >= (void *) (bh->b_data+BLOCK_SIZE)) {
			brelse(bh);
			block=bmap(inode,nr/DIR_ENTRIES_PER_BLOCK);
			if (!block) {
				nr += DIR_ENTRIES_PER_BLOCK;
				continue;
			}
			if (!(bh=bread(inode->i_dev,block)))
				return 0;
			de = (struct dir_entry *) bh->b_data;
		}
		if (de->inode) {
			brelse(bh);
			return 0;
		}
		de++;
		nr++;
	}
	brelse(bh);
	return 1;
}

int sys_rmdir(const char * name)
{
	const char * basename;
	int namelen;
	struct m_inode * dir, * inode;
	struct buffer_head * bh;
	struct dir_entry * de;

	if (!suser())
		return -EPERM;
	if (!(dir = dir_namei(name,&namelen,&basename)))
		return -ENOENT;
	if (!namelen) {
		iput(dir);
		return -ENOENT;
	}
	if (!permission(dir,MAY_WRITE)) {
		iput(dir);
		return -EPERM;
	}
	bh = find_entry(&dir,basename,namelen,&de);
	if (!bh) {
		iput(dir);
		return -ENOENT;
	}
	if (!(inode = iget(dir->i_dev, de->inode))) {
		iput(dir);
		brelse(bh);
		return -EPERM;
	}
	if ((dir->i_mode & S_ISVTX) && current->euid &&
	    inode->i_uid != current->euid) {
		iput(dir);
		iput(inode);
		brelse(bh);
		return -EPERM;
	}
	if (inode->i_dev != dir->i_dev || inode->i_count>1) {
		iput(dir);
		iput(inode);
		brelse(bh);
		return -EPERM;
	}
	if (inode == dir) {	/* we may not delete ".", but "../dir" is ok */
		iput(inode);
		iput(dir);
		brelse(bh);
		return -EPERM;
	}
	if (!S_ISDIR(inode->i_mode)) {
		iput(inode);
		iput(dir);
		brelse(bh);
		return -ENOTDIR;
	}
	if (!empty_dir(inode)) {
		iput(inode);
		iput(dir);
		brelse(bh);
		return -ENOTEMPTY;
	}
	if (inode->i_nlinks != 2)
		printk("empty directory has nlink!=2 (%d)",inode->i_nlinks);
	de->inode = 0;
	bh->b_dirt = 1;
	brelse(bh);
	inode->i_nlinks=0;
	inode->i_dirt=1;
	dir->i_nlinks--;
	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	dir->i_dirt=1;
	iput(dir);
	iput(inode);
	return 0;
}

int sys_unlink(const char * name)
{
	const char * basename;
	int namelen;
	struct m_inode * dir, * inode;
	struct buffer_head * bh;
	struct dir_entry * de;

	if (!(dir = dir_namei(name,&namelen,&basename)))
		return -ENOENT;
	if (!namelen) {
		iput(dir);
		return -ENOENT;
	}
	if (!permission(dir,MAY_WRITE)) {
		iput(dir);
		return -EPERM;
	}
	bh = find_entry(&dir,basename,namelen,&de);
	if (!bh) {
		iput(dir);
		return -ENOENT;
	}
	if (!(inode = iget(dir->i_dev, de->inode))) {
		iput(dir);
		brelse(bh);
		return -ENOENT;
	}
	if ((dir->i_mode & S_ISVTX) && !suser() &&
	    current->euid != inode->i_uid &&
	    current->euid != dir->i_uid) {
		iput(dir);
		iput(inode);
		brelse(bh);
		return -EPERM;
	}
	if (S_ISDIR(inode->i_mode)) {
		iput(inode);
		iput(dir);
		brelse(bh);
		return -EPERM;
	}
	if (!inode->i_nlinks) {
		printk("Deleting nonexistent file (%04x:%d), %d\n",
			inode->i_dev,inode->i_num,inode->i_nlinks);
		inode->i_nlinks=1;
	}
	de->inode = 0;
	bh->b_dirt = 1;
	brelse(bh);
	inode->i_nlinks--;
	inode->i_dirt = 1;
	inode->i_ctime = CURRENT_TIME;
	iput(inode);
	iput(dir);
	return 0;
}

int sys_link(const char * oldname, const char * newname)
{
	struct dir_entry * de;
	struct m_inode * oldinode, * dir;
	struct buffer_head * bh;
	const char * basename;
	int namelen;

	oldinode=namei(oldname);
	if (!oldinode)
		return -ENOENT;
	if (S_ISDIR(oldinode->i_mode)) {
		iput(oldinode);
		return -EPERM;
	}
	dir = dir_namei(newname,&namelen,&basename);
	if (!dir) {
		iput(oldinode);
		return -EACCES;
	}
	if (!namelen) {
		iput(oldinode);
		iput(dir);
		return -EPERM;
	}
	if (dir->i_dev != oldinode->i_dev) {
		iput(dir);
		iput(oldinode);
		return -EXDEV;
	}
	if (!permission(dir,MAY_WRITE)) {
		iput(dir);
		iput(oldinode);
		return -EACCES;
	}
	bh = find_entry(&dir,basename,namelen,&de);
	if (bh) {
		brelse(bh);
		iput(dir);
		iput(oldinode);
		return -EEXIST;
	}
	bh = add_entry(dir,basename,namelen,&de);
	if (!bh) {
		iput(dir);
		iput(oldinode);
		return -ENOSPC;
	}
	de->inode = oldinode->i_num;
	bh->b_dirt = 1;
	brelse(bh);
	iput(dir);
	oldinode->i_nlinks++;
	oldinode->i_ctime = CURRENT_TIME;
	oldinode->i_dirt = 1;
	iput(oldinode);
	return 0;
}