namei.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 1,434 行 · 第 1/3 页

	/*
	 * We try to drop the dentry early: we should have
	 * a usage count of 2 if we're the only user of this
	 * dentry, and if that is true (possibly after pruning
	 * the dcache), then we drop the dentry now.
	 *
	 * A low-level filesystem can, if it choses, legally
	 * do a
	 *
	 *	if (!list_empty(&dentry->d_hash))
	 *		return -EBUSY;
	 *
	 * if it cannot handle the case of removing a directory
	 * that is still in use by something else..
	 */
	switch (dentry->d_count) {
	default:
		shrink_dcache_parent(dentry);
		if (dentry->d_count != 2)
			break;
	case 2:
		d_drop(dentry);
	}

	error = dir->i_op->rmdir(dir, dentry);

	return error;
}

#ifdef OSKIT
       int do_rmdir(const char * name)
#else
static inline int do_rmdir(const char * name)
#endif
{
	int error;
	struct dentry *dir;
	struct dentry *dentry;

	dentry = lookup_dentry(name, NULL, 0);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto exit;

	error = -ENOENT;
	if (!dentry->d_inode)
		goto exit_dput;

	dir = dget(dentry->d_parent);

	/*
	 * The dentry->d_count stuff confuses d_delete() enough to
	 * not kill the inode from under us while it is locked. This
	 * wouldn't be needed, except the dentry semaphore is really
	 * in the inode, not in the dentry..
	 */
	dentry->d_count++;
	double_lock(dir, dentry);

	error = -ENOENT;
	if (check_parent(dir, dentry))
		error = vfs_rmdir(dir->d_inode, dentry);

	double_unlock(dentry, dir);
exit_dput:
	dput(dentry);
exit:
	return error;
}

asmlinkage int sys_rmdir(const char * pathname)
{
	int error;
	char * tmp;

	lock_kernel();
	tmp = getname(pathname);
	error = PTR_ERR(tmp);
	if (!IS_ERR(tmp)) {
		error = do_rmdir(tmp);
		putname(tmp);
	}
	unlock_kernel();
	return error;
}

int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
	int error;

	error = may_delete(dir, dentry, 0);
	if (!error) {
		error = -EPERM;
		if (dir->i_op && dir->i_op->unlink) {
			DQUOT_INIT(dir);
			error = dir->i_op->unlink(dir, dentry);
		}
	}
	return error;
}

#ifdef OSKIT
       int do_unlink(const char * name)
#else
static inline int do_unlink(const char * name)
#endif
{
	int error;
	struct dentry *dir;
	struct dentry *dentry;

	dentry = lookup_dentry(name, NULL, 0);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto exit;

	dir = lock_parent(dentry);
	error = -ENOENT;
	if (check_parent(dir, dentry))
		error = vfs_unlink(dir->d_inode, dentry);

        unlock_dir(dir);
	dput(dentry);
exit:
	return error;
}

asmlinkage int sys_unlink(const char * pathname)
{
	int error;
	char * tmp;

	lock_kernel();
	tmp = getname(pathname);
	error = PTR_ERR(tmp);
	if (!IS_ERR(tmp)) {
		error = do_unlink(tmp);
		putname(tmp);
	}
	unlock_kernel();
	return error;
}

#ifdef OSKIT
       int do_symlink(const char * oldname, const char * newname)
#else
static inline int do_symlink(const char * oldname, const char * newname)
#endif
{
	int error;
	struct dentry *dir;
	struct dentry *dentry;

	dentry = lookup_dentry(newname, NULL, 0);

	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto exit;

	dir = lock_parent(dentry);
	error = -ENOENT;
	if (!check_parent(dir, dentry))
		goto exit_lock;

	error = may_create(dir->d_inode, dentry);
	if (error)
		goto exit_lock;

	error = -EPERM;
	if (!dir->d_inode->i_op || !dir->d_inode->i_op->symlink)
		goto exit_lock;

	DQUOT_INIT(dir->d_inode);
	error = dir->d_inode->i_op->symlink(dir->d_inode, dentry, oldname);

exit_lock:
	unlock_dir(dir);
	dput(dentry);
exit:
	return error;
}

asmlinkage int sys_symlink(const char * oldname, const char * newname)
{
	int error;
	char * from;

	lock_kernel();
	from = getname(oldname);
	error = PTR_ERR(from);
	if (!IS_ERR(from)) {
		char * to;
		to = getname(newname);
		error = PTR_ERR(to);
		if (!IS_ERR(to)) {
			error = do_symlink(from,to);
			putname(to);
		}
		putname(from);
	}
	unlock_kernel();
	return error;
}

#ifdef OSKIT
       int do_link(struct dentry *dentry, const char * newname)
#else
static inline int do_link(const char * oldname, const char * newname)
#endif
{
	struct dentry *old_dentry, *new_dentry, *dir;
	struct inode *inode;
	int error;

	/*
	 * Hardlinks are often used in delicate situations.  We avoid
	 * security-related surprises by not following symlinks on the
	 * newname.  --KAB
	 *
	 * We don't follow them on the oldname either to be compatible
	 * with linux 2.0, and to avoid hard-linking to directories
	 * and other special files.  --ADM
	 */
#ifdef OSKIT
	dget(dentry);
	old_dentry = dentry;
#else
	old_dentry = lookup_dentry(oldname, NULL, 0);
#endif
	error = PTR_ERR(old_dentry);
	if (IS_ERR(old_dentry))
		goto exit;

	new_dentry = lookup_dentry(newname, NULL, 0);
	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto exit_old;

	dir = lock_parent(new_dentry);
	error = -ENOENT;
	if (!check_parent(dir, new_dentry))
		goto exit_lock;

	error = -ENOENT;
	inode = old_dentry->d_inode;
	if (!inode)
		goto exit_lock;

	error = may_create(dir->d_inode, new_dentry);
	if (error)
		goto exit_lock;

	error = -EXDEV;
	if (dir->d_inode->i_dev != inode->i_dev)
		goto exit_lock;

	/*
	 * A link to an append-only or immutable file cannot be created.
	 */
	error = -EPERM;
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		goto exit_lock;

	error = -EPERM;
	if (!dir->d_inode->i_op || !dir->d_inode->i_op->link)
		goto exit_lock;

	DQUOT_INIT(dir->d_inode);
	error = dir->d_inode->i_op->link(old_dentry, dir->d_inode, new_dentry);

exit_lock:
	unlock_dir(dir);
	dput(new_dentry);
exit_old:
	dput(old_dentry);
exit:
	return error;
}

#ifndef OSKIT
asmlinkage int sys_link(const char * oldname, const char * newname)
{
	int error;
	char * from;

	lock_kernel();
	from = getname(oldname);
	error = PTR_ERR(from);
	if (!IS_ERR(from)) {
		char * to;
		to = getname(newname);
		error = PTR_ERR(to);
		if (!IS_ERR(to)) {
			error = do_link(from,to);
			putname(to);
		}
		putname(from);
	}
	unlock_kernel();
	return error;
}
#endif

int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;
	int need_rehash = 0;

	if (old_dentry->d_inode == new_dentry->d_inode)
		return 0;

	error = may_delete(old_dir, old_dentry, 1);
	if (error)
		return error;

	if (new_dir->i_dev != old_dir->i_dev)
		return -EXDEV;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry);
	else
		error = may_delete(new_dir, new_dentry, 1);
	if (error)
		return error;

	if (!old_dir->i_op || !old_dir->i_op->rename)
		return -EPERM;

	/*
	 * If we are going to change the parent - check write permissions,
	 * we'll need to flip '..'.
	 */
	if (new_dir != old_dir) {
		error = permission(old_dentry->d_inode, MAY_WRITE);
	}
	if (error)
		return error;

	DQUOT_INIT(old_dir);
	DQUOT_INIT(new_dir);
	down(&old_dir->i_sb->s_vfs_rename_sem);
	error = -EINVAL;
	if (is_subdir(new_dentry, old_dentry))
		goto out_unlock;
	if (new_dentry->d_inode) {
		error = -EBUSY;
		if (d_invalidate(new_dentry)<0)
			goto out_unlock;
		need_rehash = 1;
	}
	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (need_rehash)
		d_rehash(new_dentry);
	if (!error)
		d_move(old_dentry,new_dentry);
out_unlock:
	up(&old_dir->i_sb->s_vfs_rename_sem);
	return error;
}

int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;

	if (old_dentry->d_inode == new_dentry->d_inode)
		return 0;

	error = may_delete(old_dir, old_dentry, 0);
	if (error)
		return error;

	if (new_dir->i_dev != old_dir->i_dev)
		return -EXDEV;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry);
	else
		error = may_delete(new_dir, new_dentry, 0);
	if (error)
		return error;

	if (!old_dir->i_op || !old_dir->i_op->rename)
		return -EPERM;

	DQUOT_INIT(old_dir);
	DQUOT_INIT(new_dir);
	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		return error;
	/* The following d_move() should become unconditional */
	if (!(old_dir->i_sb->s_flags & MS_ODD_RENAME)) {
		d_move(old_dentry, new_dentry);
	}
	return 0;
}

int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	if (S_ISDIR(old_dentry->d_inode->i_mode))
		return vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
	else
		return vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
}

#ifdef OSKIT
       int do_rename(const char * oldname, const char * newname)
#else
static inline int do_rename(const char * oldname, const char * newname)
#endif
{
	int error;
	struct dentry * old_dir, * new_dir;
	struct dentry * old_dentry, *new_dentry;

	old_dentry = lookup_dentry(oldname, NULL, 0);

	error = PTR_ERR(old_dentry);
	if (IS_ERR(old_dentry))
		goto exit;

	error = -ENOENT;
	if (!old_dentry->d_inode)
		goto exit_old;

	{
		unsigned int flags = 0;
		if (S_ISDIR(old_dentry->d_inode->i_mode))
			flags = LOOKUP_SLASHOK;
		new_dentry = lookup_dentry(newname, NULL, flags);
	}

	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto exit_old;

	new_dir = get_parent(new_dentry);
	old_dir = get_parent(old_dentry);

	double_lock(new_dir, old_dir);

	error = -ENOENT;
	if (check_parent(old_dir, old_dentry) && check_parent(new_dir, new_dentry))
		error = vfs_rename(old_dir->d_inode, old_dentry,
				   new_dir->d_inode, new_dentry);

	double_unlock(new_dir, old_dir);
	dput(new_dentry);
exit_old:
	dput(old_dentry);
exit:
	return error;
}

asmlinkage int sys_rename(const char * oldname, const char * newname)
{
	int error;
	char * from;

	lock_kernel();
	from = getname(oldname);
	error = PTR_ERR(from);
	if (!IS_ERR(from)) {
		char * to;
		to = getname(newname);
		error = PTR_ERR(to);
		if (!IS_ERR(to)) {
			error = do_rename(from,to);
			putname(to);
		}
		putname(from);
	}
	unlock_kernel();
	return error;
}