what is kernel file stuct

struct file {
	spinlock_t			f_lock;
	fmode_t				f_mode;
	const struct file_operations	*f_op;
	struct address_space		*f_mapping;
	void				*private_data;
	struct inode			*f_inode;
	unsigned int			f_flags;
	unsigned int			f_iocb_flags;
	const struct cred		*f_cred;
	struct fown_struct		*f_owner;
	/* --- cacheline 1 boundary (64 bytes) --- */
	union {
		const struct path	f_path;
		struct path		__f_path;
	};
	union {
		/* regular files (with FMODE_ATOMIC_POS) and directories */
		struct mutex		f_pos_lock;
		/* pipes */
		u64			f_pipe;
	};
	loff_t				f_pos;
#ifdef CONFIG_SECURITY
	void				*f_security;
#endif
	/* --- cacheline 2 boundary (128 bytes) --- */
	errseq_t			f_wb_err;
	errseq_t			f_sb_err;
#ifdef CONFIG_EPOLL
	struct hlist_head		*f_ep;
#endif
	union {
		struct callback_head	f_task_work;
		struct llist_node	f_llist;
		struct file_ra_state	f_ra;
		freeptr_t		f_freeptr;
	};
	file_ref_t			f_ref;
	/* --- cacheline 3 boundary (192 bytes) --- */
} __randomize_layout
  __attribute__((aligned(4)));	/* lest something weird decides that 2 is OK */