29 struct loop_device {  struct
35 	int		(*transfer)(struct loop_device *, int cmd,  argument
46 	int		(*ioctl)(struct loop_device *, int cmd,   argument
49 	struct file *	lo_backing_file;
50 	struct block_device *lo_device;
51 	void		*key_data; 
53 	gfp_t		old_gfp_mask;
55 	spinlock_t		lo_lock;
56 	int			lo_state;
57 	struct mutex		lo_ctl_mutex;
81 	int (*transfer)(struct loop_device *lo, int cmd,  argument