66 lines
1 KiB
C
66 lines
1 KiB
C
#include "types.h"
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#include "param.h"
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#include "x86.h"
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#include "mmu.h"
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#include "proc.h"
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#include "defs.h"
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#include "spinlock.h"
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#include "buf.h"
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struct buf buf[NBUF];
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struct spinlock buf_table_lock = { "buf_table" };
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struct buf *
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getblk()
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{
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int i;
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acquire(&buf_table_lock);
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// XXX need to lock the block even if not caching, to
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// avoid read modify write problems.
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while(1){
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for(i = 0; i < NBUF; i++){
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if((buf[i].flags & B_BUSY) == 0){
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buf[i].flags |= B_BUSY;
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release(&buf_table_lock);
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return buf + i;
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}
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}
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sleep(buf, &buf_table_lock);
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}
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}
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struct buf *
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bread(uint dev, uint sector)
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{
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void *c;
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struct buf *b;
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extern struct spinlock ide_lock;
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b = getblk();
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acquire(&ide_lock);
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c = ide_start_read(dev & 0xff, sector, b->data, 1);
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sleep (c, &ide_lock);
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ide_finish_read(c);
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release(&ide_lock);
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return b;
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}
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void
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brelse(struct buf *b)
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{
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if((b->flags & B_BUSY) == 0)
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panic("brelse");
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acquire(&buf_table_lock);
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b->flags &= ~B_BUSY;
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wakeup(buf);
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release(&buf_table_lock);
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}
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