#ifndef _BLK_H#define _BLK_H#define NR_BLK_DEV	7/* * NR_REQUEST is the number of entries in the request-queue. * NOTE that writes may use only the low 2/3 of these: reads * take precedence. * * 32 seems to be a reasonable number: enough to get some benefit * from the elevator-mechanism, but not so much as to lock a lot of * buffers when they are in the queue. 64 seems to be too many (easily * long pauses in reading when heavy writing/syncing is going on) */#define NR_REQUEST	32/* * Ok, this is an expanded form so that we can use the same * request for paging requests when that is implemented. In * paging, 'bh' is NULL, and 'waiting' is used to wait for * read/write completion. */struct request {	int dev;		/* -1 if no request */	int cmd;		/* READ or WRITE */	int errors;	unsigned long sector;	unsigned long nr_sectors;	char * buffer;	struct task_struct * waiting;	struct buffer_head * bh;	struct request * next;};/* * This is used in the elevator algorithm: Note that * reads always go before writes. This is natural: reads * are much more time-critical than writes. */#define IN_ORDER(s1,s2) \((s1)->cmd<(s2)->cmd || (s1)->cmd==(s2)->cmd && \((s1)->dev < (s2)->dev || ((s1)->dev == (s2)->dev && \(s1)->sector < (s2)->sector)))struct blk_dev_struct {	void (*request_fn)(void);	struct request * current_request;};extern struct blk_dev_struct blk_dev[NR_BLK_DEV];extern struct request request[NR_REQUEST];extern struct task_struct * wait_for_request;#ifdef MAJOR_NR/* * Add entries as needed. Currently the only block devices * supported are hard-disks and floppies. */#if (MAJOR_NR == 1)/* ram disk */#define DEVICE_NAME "ramdisk"#define DEVICE_REQUEST do_rd_request#define DEVICE_NR(device) ((device) & 7)#define DEVICE_ON(device) #define DEVICE_OFF(device)#elif (MAJOR_NR == 2)/* floppy */#define DEVICE_NAME "floppy"#define DEVICE_INTR do_floppy#define DEVICE_REQUEST do_fd_request#define DEVICE_NR(device) ((device) & 3)#define DEVICE_ON(device) floppy_on(DEVICE_NR(device))#define DEVICE_OFF(device) floppy_off(DEVICE_NR(device))#elif (MAJOR_NR == 3)/* harddisk */#define DEVICE_NAME "harddisk"#define DEVICE_INTR do_hd#define DEVICE_REQUEST do_hd_request#define DEVICE_NR(device) (MINOR(device)/5)#define DEVICE_ON(device)#define DEVICE_OFF(device)#elif/* unknown blk device */#error "unknown blk device"#endif#define CURRENT (blk_dev[MAJOR_NR].current_request)#define CURRENT_DEV DEVICE_NR(CURRENT->dev)#ifdef DEVICE_INTRvoid (*DEVICE_INTR)(void) = NULL;#endifstatic void (DEVICE_REQUEST)(void);extern inline void unlock_buffer(struct buffer_head * bh){	if (!bh->b_lock)		printk(DEVICE_NAME ": free buffer being unlocked\n");	bh->b_lock=0;	wake_up(&bh->b_wait);}extern inline void end_request(int uptodate){	DEVICE_OFF(CURRENT->dev);	if (CURRENT->bh) {		CURRENT->bh->b_uptodate = uptodate;		unlock_buffer(CURRENT->bh);	}	if (!uptodate) {		printk(DEVICE_NAME " I/O error\n\r");		printk("dev %04x, block %d\n\r",CURRENT->dev,			CURRENT->bh->b_blocknr);	}	wake_up(&CURRENT->waiting);	wake_up(&wait_for_request);	CURRENT->dev = -1;	CURRENT = CURRENT->next;}#define INIT_REQUEST \repeat: \	if (!CURRENT) \		return; \	if (MAJOR(CURRENT->dev) != MAJOR_NR) \		panic(DEVICE_NAME ": request list destroyed"); \	if (CURRENT->bh) { \		if (!CURRENT->bh->b_lock) \			panic(DEVICE_NAME ": block not locked"); \	}#endif#endif