nilfs_inode_by_name
res = nilfs_inode_by_name(d_inode(child), &dotdot_name, &ino);
res = nilfs_inode_by_name(dir, &dentry->d_name, &ino);
int nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr, ino_t *ino);