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