FILE* 文件指针和文件描述符

/usr/src/kernels/2.6.18-238.el5-x86_64/include/linux/fs.h

struct file {
        /*
         * fu_list becomes invalid after file_free is called and queued via
         * fu_rcuhead for RCU freeing
         */
        union {
                struct list_head        fu_list;
                struct rcu_head         fu_rcuhead;
        } f_u;
        struct dentry *f_dentry;
        struct vfsmount *f_vfsmnt;
        const struct file_operations *f_op;
        atomic_t                f_count;
        unsigned int f_flags;
        mode_t                  f_mode;
        loff_t                  f_pos;
        struct fown_struct      f_owner;
        unsigned int f_uid, f_gid;
        struct file_ra_state    f_ra;

        unsigned long           f_version;
        void *f_security;

        /* 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;
        spinlock_t              f_ep_lock;
#endif /* #ifdef CONFIG_EPOLL */
        struct address_space *f_mapping;
};