82 typedef struct	buf {  struct
84 	struct buf *b_forw;		/* headed by d_tab of conf.c */  argument
85 	struct buf *b_back;		/*  "  */  argument
86 	struct buf *av_forw;		/* position on free list, */  argument
87 	struct buf *av_back;		/* if not BUSY */  argument
88 	o_dev_t	b_dev;			/* OLD major+minor device name */
89 	size_t b_bcount;		/* transfer count */
90 	union {
117 	size_t	b_bufsize;		/* size of allocated buffer */  argument
118 	int	(*b_iodone)(struct buf *);	/* function called by iodone */  argument
120 	struct 	buf *b_chain;		/* chain together all buffers here */  argument
125 	ksema_t	b_sem;			/* Exclusive access to buf */  argument
127 	struct buf *b_list;		/* List of potential B_DELWRI bufs */  argument
130 	struct vnode *b_file;		/* file associated with this buffer */  argument
131 	offset_t b_offset;		/* offset in file assoc. with buffer */  argument
141 	struct buf *b_forw, *b_back;	/* queue of unit queues */  argument