虚函数效率真的低吗？ 第1页

       struct file {  union {   struct llist_node fu_llist;   struct rcu_head  fu_rcuhead;  } f_u;  struct path  f_path;  struct inode  *f_inode; /* cached value */  const struct file_operations *f_op;   /*   * Protects f_ep_links, f_flags.   * Must not be taken from IRQ context.   */  spinlock_t  f_lock;  enum rw_hint  f_write_hint;  atomic_long_t  f_count;  unsigned int   f_flags;  fmode_t   f_mode;  struct mutex  f_pos_lock;  loff_t   f_pos;  struct fown_struct f_owner;  const struct cred *f_cred;  struct file_ra_state f_ra;   u64   f_version; #ifdef CONFIG_SECURITY  void   *f_security; #endif  /* needed for tty driver, and maybe others */  void   *private_data;  #ifdef CONFIG_EPOLL  /* Used by fs/eventpoll.c to link all the hooks to this file */  struct list_head f_ep_links;  struct list_head f_tfile_llink; #endif /* #ifdef CONFIG_EPOLL */  struct address_space *f_mapping;  errseq_t  f_wb_err;  errseq_t  f_sb_err; /* for syncfs */ } __randomize_layout   __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */     

       struct file_operations {  struct module *owner;  loff_t (*llseek) (struct file *, loff_t, int);  ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);  ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);  ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);  ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);  int (*iopoll)(struct kiocb *kiocb, bool spin);  int (*iterate) (struct file *, struct dir_context *);  int (*iterate_shared) (struct file *, struct dir_context *);  __poll_t (*poll) (struct file *, struct poll_table_struct *);  long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);  long (*compat_ioctl) (struct file *, unsigned int, unsigned long);  int (*mmap) (struct file *, struct vm_area_struct *);  unsigned long mmap_supported_flags;  int (*open) (struct inode *, struct file *);  int (*flush) (struct file *, fl_owner_t id);  int (*release) (struct inode *, struct file *);  int (*fsync) (struct file *, loff_t, loff_t, int datasync);  int (*fasync) (int, struct file *, int);  int (*lock) (struct file *, int, struct file_lock *);  ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);  unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);  int (*check_flags)(int);  int (*flock) (struct file *, int, struct file_lock *);  ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);  ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);  int (*setlease)(struct file *, long, struct file_lock **, void **);  long (*fallocate)(struct file *file, int mode, loff_t offset,      loff_t len);  void (*show_fdinfo)(struct seq_file *m, struct file *f); #ifndef CONFIG_MMU  unsigned (*mmap_capabilities)(struct file *); #endif  ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,    loff_t, size_t, unsigned int);  loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,        struct file *file_out, loff_t pos_out,        loff_t len, unsigned int remap_flags);  int (*fadvise)(struct file *, loff_t, loff_t, int); } __randomize_layout;