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bio.c: use struct like icache does

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rsc 2009-05-31 01:29:17 +00:00
parent c47bc4fd54
commit 0badeaa29f
1 changed files with 31 additions and 30 deletions
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57
bio.c
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@ -27,30 +27,32 @@
#include "spinlock.h"
#include "buf.h"
struct {
struct spinlock lock;
struct buf buf[NBUF];
struct spinlock buf_table_lock;
// Linked list of all buffers, through prev/next.
// bufhead->next is most recently used.
// bufhead->tail is least recently used.
struct buf bufhead;
// head.next is most recently used.
struct buf head;
} bcache;
void
binit(void)
{
struct buf *b;
initlock(&buf_table_lock, "buf_table");
initlock(&bcache.lock, "buf_table");
//PAGEBREAK!
// Create linked list of buffers
bufhead.prev = &bufhead;
bufhead.next = &bufhead;
for(b = buf; b < buf+NBUF; b++){
b->next = bufhead.next;
b->prev = &bufhead;
bufhead.next->prev = b;
bufhead.next = b;
bcache.head.prev = &bcache.head;
bcache.head.next = &bcache.head;
for(b = bcache.buf; b < bcache.buf+NBUF; b++){
b->next = bcache.head.next;
b->prev = &bcache.head;
b->dev = -1;
bcache.head.next->prev = b;
bcache.head.next = b;
}
}
@ -62,30 +64,29 @@ bget(uint dev, uint sector)
{
struct buf *b;
acquire(&buf_table_lock);
acquire(&bcache.lock);
loop:
// Try for cached block.
for(b = bufhead.next; b != &bufhead; b = b->next){
if((b->flags & (B_BUSY|B_VALID)) &&
b->dev == dev && b->sector == sector){
for(b = bcache.head.next; b != &bcache.head; b = b->next){
if(b->dev == dev && b->sector == sector){
if(!(b->flags & B_BUSY)){
b->flags |= B_BUSY;
release(&buf_table_lock);
release(&bcache.lock);
return b;
}
sleep(b, &buf_table_lock);
sleep(b, &bcache.lock);
goto loop;
}
}
// Allocate fresh block.
for(b = bufhead.prev; b != &bufhead; b = b->prev){
for(b = bcache.head.prev; b != &bcache.head; b = b->prev){
if((b->flags & B_BUSY) == 0){
b->dev = dev;
b->sector = sector;
b->flags = B_BUSY;
release(&buf_table_lock);
release(&bcache.lock);
return b;
}
}
@ -104,7 +105,7 @@ bread(uint dev, uint sector)
return b;
}
// Write buf's contents to disk. Must be locked.
// Write b's contents to disk. Must be locked.
void
bwrite(struct buf *b)
{
@ -114,25 +115,25 @@ bwrite(struct buf *b)
iderw(b);
}
// Release the buffer buf.
// Release the buffer b.
void
brelse(struct buf *b)
{
if((b->flags & B_BUSY) == 0)
panic("brelse");
acquire(&buf_table_lock);
acquire(&bcache.lock);
b->next->prev = b->prev;
b->prev->next = b->next;
b->next = bufhead.next;
b->prev = &bufhead;
bufhead.next->prev = b;
bufhead.next = b;
b->next = bcache.head.next;
b->prev = &bcache.head;
bcache.head.next->prev = b;
bcache.head.next = b;
b->flags &= ~B_BUSY;
wakeup(b);
release(&buf_table_lock);
release(&bcache.lock);
}