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提交 ba2fdf81 创建 作者: Nickolai Zeldovich's avatar Nickolai Zeldovich
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use namespaces for buffer cache (possibly broken)

上级 27e046f9
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正在显示 包含 67 行增加 和 48 行删除
bio.c
浏览文件 @ ba2fdf81
......@@ -28,36 +28,47 @@
#include "condvar.h"
#include "buf.h"
struct {
struct spinlock lock;
struct buf buf[NBUF];
// Linked list of all buffers, through prev/next.
// head.next is most recently used.
struct buf head;
} bcache;
static struct ns *bufns;
void
binit(void)
{
struct buf *b;
initlock(&bcache.lock, "bcache");
//PAGEBREAK!
// Create linked list of buffers
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;
bufns = nsalloc(0);
for (uint i = 0; i < NBUF; i++) {
struct buf *b = kmalloc(sizeof(*b));
b->dev = 0xdeadbeef;
b->sector = -i; /* dummy to pre-allocate NBUF spaces for evict */
b->flags = 0;
initlock(&b->lock, "bcache-lock");
initcondvar(&b->cv, "bcache-cv");
if (ns_insert(bufns, b->sector, b) < 0)
panic("binit ns_insert");
}
}
static void *
evict(uint key, void *bp)
{
struct buf *b = bp;
acquire(&b->lock);
if ((b->flags & (B_BUSY | B_VALID)) == 0)
return b;
release(&b->lock);
return 0;
}
static void *
evict_valid(uint key, void *bp)
{
struct buf *b = bp;
acquire(&b->lock);
if ((b->flags & B_BUSY) == 0)
return b;
release(&b->lock);
return 0;
}
// Look through buffer cache for sector on device dev.
// If not found, allocate fresh block.
// In either case, return locked buffer.
......@@ -66,33 +77,50 @@ bget(uint dev, uint sector)
{
struct buf *b;
acquire(&bcache.lock);
loop:
// Try for cached block.
for(b = bcache.head.next; b != &bcache.head; b = b->next){
if(b->dev == dev && b->sector == sector){
if(!(b->flags & B_BUSY)){
// XXX ignore dev
rcu_begin_read();
b = ns_lookup(bufns, sector);
if (b) {
acquire(&b->lock);
if (b->dev != dev)
panic("dev mismatch");
if (!(b->flags & B_BUSY)) {
b->flags |= B_BUSY;
release(&bcache.lock);
release(&b->lock);
rcu_end_read();
return b;
}
cv_sleep(&b->cv, &bcache.lock);
cv_sleep(&b->cv, &b->lock);
release(&b->lock);
goto loop;
}
}
rcu_end_read();
// Allocate fresh block.
for(b = bcache.head.prev; b != &bcache.head; b = b->prev){
if((b->flags & B_BUSY) == 0){
struct buf *victim = ns_enumerate(bufns, evict);
if (victim == 0)
victim = ns_enumerate(bufns, evict_valid);
if (victim == 0)
panic("bget all busy");
victim->flags |= B_BUSY;
ns_remove(bufns, victim->sector, victim);
release(&victim->lock);
rcu_delayed(victim, kmfree);
b = kmalloc(sizeof(*b));
b->dev = dev;
b->sector = sector;
b->flags = B_BUSY;
release(&bcache.lock);
return b;
}
initlock(&b->lock, "bcache-lock");
initcondvar(&b->cv, "bcache-cv");
if (ns_insert(bufns, b->sector, b) < 0) {
rcu_delayed(b, kmfree);
goto loop;
}
panic("bget: no buffers");
return b;
}
// Return a B_BUSY buf with the contents of the indicated disk sector.
......@@ -121,21 +149,11 @@ bwrite(struct buf *b)
void
brelse(struct buf *b)
{
acquire(&b->lock);
if((b->flags & B_BUSY) == 0)
panic("brelse");
acquire(&bcache.lock);
b->next->prev = b->prev;
b->prev->next = b->next;
b->next = bcache.head.next;
b->prev = &bcache.head;
bcache.head.next->prev = b;
bcache.head.next = b;
b->flags &= ~B_BUSY;
release(&b->lock);
cv_wakeup(&b->cv);
release(&bcache.lock);
}
buf.h
浏览文件 @ ba2fdf81
......@@ -6,6 +6,7 @@ struct buf {
struct buf *next;
struct buf *qnext; // disk queue
struct condvar cv;
struct spinlock lock;
uchar data[512];
};
#define B_BUSY 0x1 // buffer is locked by some process
......
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