126 lines
2.3 KiB
C
126 lines
2.3 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;
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// linked list of all buffers, through prev/next.
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// bufhead->next is most recently used.
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// bufhead->tail is least recently used.
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struct buf bufhead;
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void
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binit(void)
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{
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struct buf *b;
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initlock(&buf_table_lock, "buf_table");
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bufhead.prev = &bufhead;
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bufhead.next = &bufhead;
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for(b = buf; b < buf+NBUF; b++){
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b->next = bufhead.next;
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b->prev = &bufhead;
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bufhead.next->prev = b;
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bufhead.next = b;
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}
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}
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struct buf *
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getblk(uint dev, uint sector)
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{
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struct buf *b;
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acquire(&buf_table_lock);
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while(1){
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for(b = bufhead.next; b != &bufhead; b = b->next)
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if((b->flags & (B_BUSY|B_VALID)) && b->dev == dev && b->sector == sector)
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break;
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if(b != &bufhead){
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if(b->flags & B_BUSY){
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sleep(buf, &buf_table_lock);
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} else {
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b->flags |= B_BUSY;
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release(&buf_table_lock);
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return b;
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}
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} else {
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for(b = bufhead.prev; b != &bufhead; b = b->prev){
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if((b->flags & B_BUSY) == 0){
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b->flags = B_BUSY;
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b->dev = dev;
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b->sector = sector;
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release(&buf_table_lock);
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return b;
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}
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}
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panic("getblk: no buffers");
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}
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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(dev, sector);
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if(b->flags & B_VALID){
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return b;
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}
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acquire(&ide_lock);
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c = ide_start_rw(dev & 0xff, sector, b->data, 1, 1);
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sleep (c, &ide_lock);
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ide_finish(c);
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b->flags |= B_VALID;
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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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bwrite(struct buf *b, uint sector)
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{
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void *c;
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extern struct spinlock ide_lock;
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acquire(&ide_lock);
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c = ide_start_rw(b->dev & 0xff, sector, b->data, 1, 0);
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sleep (c, &ide_lock);
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ide_finish(c);
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b->flags |= B_VALID;
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release(&ide_lock);
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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->next->prev = b->prev;
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b->prev->next = b->next;
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b->next = bufhead.next;
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b->prev = &bufhead;
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bufhead.next->prev = b;
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bufhead.next = b;
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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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