/*
 * These are some of Linux's base filesystem abstractions, as 
 * taken from include/linux/fs.h
 */

/*
 * This is the inode structure.  Any filesystem object: Files in 
 * filesystems, devices, sockets, pipes, etc. are all represented by
 * inodes.
 */
struct inode {
	kdev_t		i_dev;
	unsigned long	i_ino;
	umode_t		i_mode;
	nlink_t		i_nlink;
	uid_t		i_uid;
	gid_t		i_gid;
	kdev_t		i_rdev;
	off_t		i_size;
	time_t		i_atime;
	time_t		i_mtime;
	time_t		i_ctime;
	unsigned long	i_blksize;
	unsigned long	i_blocks;
	unsigned long	i_version;
	unsigned long	i_nrpages;
	struct semaphore i_sem;
	struct inode_operations *i_op;
	struct super_block *i_sb;
	struct wait_queue *i_wait;
	struct file_lock *i_flock;
	struct vm_area_struct *i_mmap;
	struct page *i_pages;
	struct dquot *i_dquot[MAXQUOTAS];
	struct inode *i_next, *i_prev;
	struct inode *i_hash_next, *i_hash_prev;
	struct inode *i_bound_to, *i_bound_by;
	struct inode *i_mount;
	unsigned short i_count;
	unsigned short i_flags;
	unsigned char i_lock;
	unsigned char i_dirt;
	unsigned char i_pipe;
	unsigned char i_sock;
	unsigned char i_seek;
	unsigned char i_update;
	unsigned short i_writecount;
	union {
		struct pipe_inode_info pipe_i;
		struct minix_inode_info minix_i;
		struct ext_inode_info ext_i;
		struct ext2_inode_info ext2_i;
		struct hpfs_inode_info hpfs_i;
		struct msdos_inode_info msdos_i;
		struct umsdos_inode_info umsdos_i;
		struct iso_inode_info isofs_i;
		struct nfs_inode_info nfs_i;
		struct xiafs_inode_info xiafs_i;
		struct sysv_inode_info sysv_i;
		struct affs_inode_info affs_i;
		struct ufs_inode_info ufs_i;
		struct socket socket_i;
		void * generic_ip;
	} u;
};

/*
 * ...and these are the operations you can perform on an inode.  Each
 * different kind of inode will have its own inode operations table.
 * 
 * This structure is in effect the virtual function table for a
 * "sub-class" of the inode superclass, where examples of subclasses
 * of the inode superclass would include ext2 inodes, msdos inodes,
 * pipes, tty devices, etc.
 */
struct inode_operations {
	struct file_operations * default_file_ops;
	int (*create) (struct inode *,const char *,int,int,struct inode **);
	int (*lookup) (struct inode *,const char *,int,struct inode **);
	int (*link) (struct inode *,struct inode *,const char *,int);
	int (*unlink) (struct inode *,const char *,int);
	int (*symlink) (struct inode *,const char *,int,const char *);
	int (*mkdir) (struct inode *,const char *,int,int);
	int (*rmdir) (struct inode *,const char *,int);
	int (*mknod) (struct inode *,const char *,int,int,int);
	int (*rename) (struct inode *,const char *,int,
		       struct inode *,const char *,int, int);
	int (*readlink) (struct inode *,char *,int);
	int (*follow_link) (struct inode *,struct inode *,int,
			    int,struct inode **);
	int (*readpage) (struct inode *, struct page *);
	int (*writepage) (struct inode *, struct page *);
	int (*bmap) (struct inode *,int);
	void (*truncate) (struct inode *);
	int (*permission) (struct inode *, int);
	int (*smap) (struct inode *,int);
};

/*
 * Struct file represents an open file object.  Two file descriptors
 * can point to the same "struct file" if one was created using dup()
 * or dup2() of the first file descriptor.
 */
struct file {
	mode_t f_mode;
	loff_t f_pos;
	unsigned short f_flags;
	unsigned short f_count;
	unsigned long f_reada, f_ramax, f_raend, f_ralen, f_rawin;
	struct file *f_next, *f_prev;
	int f_owner;		/* pid or -pgrp where SIGIO should be sent */
	struct inode * f_inode;
	struct file_operations * f_op;
	unsigned long f_version;
	void *private_data;	/* needed for tty driver, and maybe others */
};

/*
 * These are the file operations.  Like the inode operations, each
 * different class of inode will tend to have a different file
 * operations pointer.  In some cases, the file operations may change
 * over time (for example, when a tty hangup happens and the tty
 * access revokes access to exsting file descriptors).
 */	
struct file_operations {
	int (*lseek) (struct inode *, struct file *, off_t, int);
	int (*read) (struct inode *, struct file *, char *, int);
	int (*write) (struct inode *, struct file *, const char *, int);
	int (*readdir) (struct inode *, struct file *, void *, filldir_t);
	int (*select) (struct inode *, struct file *, int, select_table *);
	int (*ioctl) (struct inode *, struct file *, 
		      unsigned int, unsigned long);
	int (*mmap) (struct inode *, struct file *, struct vm_area_struct *);
	int (*open) (struct inode *, struct file *);
	void (*release) (struct inode *, struct file *);
	int (*fsync) (struct inode *, struct file *);
	int (*fasync) (struct inode *, struct file *, int);
	int (*check_media_change) (kdev_t dev);
	int (*revalidate) (kdev_t dev);
};