kernel source코드중 이런건 어떻게 해석하나요?

const struct inode_operations ext4_dir_inode_operations = {
	.create		= ext4_create,
	.lookup		= ext4_lookup,
	.link		= ext4_link,
	.unlink		= ext4_unlink,
	.symlink	= ext4_symlink,
	.mkdir		= ext4_mkdir,
	.rmdir		= ext4_rmdir,
	.mknod		= ext4_mknod,
	.tmpfile	= ext4_tmpfile,
	.rename		= ext4_rename2,
	.setattr	= ext4_setattr,
	.getattr	= ext4_getattr,
	.listxattr	= ext4_listxattr,
	.get_acl	= ext4_get_acl,
	.set_acl	= ext4_set_acl,
	.fiemap         = ext4_fiemap,
};

static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
	struct inode *inode;
	struct ext4_dir_entry_2 *de;
	struct buffer_head *bh;
 
	if (ext4_encrypted_inode(dir)) {
		int res = fscrypt_get_encryption_info(dir);
 
		/*
		 * DCACHE_ENCRYPTED_WITH_KEY is set if the dentry is
		 * created while the directory was encrypted and we
		 * have access to the key.
		 */
		if (fscrypt_has_encryption_key(dir))
			fscrypt_set_encrypted_dentry(dentry);
		fscrypt_set_d_op(dentry);
		if (res && res != -ENOKEY)
			return ERR_PTR(res);
	}
 
       if (dentry->d_name.len > EXT4_NAME_LEN)
	       return ERR_PTR(-ENAMETOOLONG);
 
	bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
	if (IS_ERR(bh))
		return (struct dentry *) bh;
	inode = NULL;
	if (bh) {
		__u32 ino = le32_to_cpu(de->inode);
		brelse(bh);
		if (!ext4_valid_inum(dir->i_sb, ino)) {
			EXT4_ERROR_INODE(dir, "bad inode number: %u", ino);
			return ERR_PTR(-EFSCORRUPTED);
		}
		if (unlikely(ino == dir->i_ino)) {
			EXT4_ERROR_INODE(dir, "'%pd' linked to parent dir",
					 dentry);
			return ERR_PTR(-EFSCORRUPTED);
		}
		inode = ext4_iget_normal(dir->i_sb, ino);
		if (inode == ERR_PTR(-ESTALE)) {
			EXT4_ERROR_INODE(dir,
					 "deleted inode referenced: %u",
					 ino);
			return ERR_PTR(-EFSCORRUPTED);
		}
		if (!IS_ERR(inode) && ext4_encrypted_inode(dir) &&
		    (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) &&
		    !fscrypt_has_permitted_context(dir, inode)) {
			ext4_warning(inode->i_sb,
				     "Inconsistent encryption contexts: %lu/%lu",
				     dir->i_ino, inode->i_ino);
			iput(inode);
			return ERR_PTR(-EPERM);
		}
	}
	return d_splice_alias(inode, dentry);
}