/* look buffer up from buffer cache; dev is buffer-device ID, not system */
struct bufblk *
buffindblk(long dev, off_t num, long rel)
{
#if (BUFNEWHASH)
bufval_t val = bufmkhashkey(dev, num);
bufval_t key = bufhash(val);
struct bufblk *blk;
struct bufchain *chain = &bufhash[key];
#else
bufval_t key = bufhash(num);
long dkey = dev & BUFDEVMASK;
struct bufblk *blk = NULL;
#endif
#if (BUFNEWHASH)
fmtxlk(&chain->lk);
blk = chain->list;
while ((blk) && blk->num != num) {
blk = blk->tabnext;
}
if ((blk) && (rel)) {
/* remove block from buffer hash chain */
if (blk->tabprev) {
blk->tabprev->tabnext = blk->tabnext;
} else {
chain->list = blk->tabnext;
}
if (blk->tabnext) {
blk->tabnext->tabprev = blk->tabprev;
}
}
return blk;
#else
fmtxlk(&buflktab[dkey]);
blk = bufhash[dkey][key];
while ((blk) && blk->num != num) {
blk = blk->tabnext;
}
if ((blk) && (rel)) {
/* remove block from buffer hash chain */
if (blk->tabprev) {
blk->tabprev->tabnext = blk->tabnext;
} else {
bufhash[dkey][key] = blk->tabnext;
}
if (blk->tabnext) {
blk->tabnext->tabprev = blk->tabprev;
}
}
fmtxunlk(&buflktab[dkey]);
return blk;
#endif
}
static void insert_into_hashtable(struct bufpool *pool, struct buf *buf)
{
int slot;
slot = bufhash(buf->blkno) % BUFPOOL_HASHSIZE;
if (pool->hashtable[slot]) pool->hashtable[slot]->bucket.prev = buf;
buf->bucket.next = pool->hashtable[slot];
buf->bucket.prev = NULL;
pool->hashtable[slot] = buf;
}
static void remove_from_hashtable(struct bufpool *pool, struct buf *buf)
{
int slot;
slot = bufhash(buf->blkno) % BUFPOOL_HASHSIZE;
if (buf->bucket.next) buf->bucket.next->bucket.prev = buf->bucket.prev;
if (buf->bucket.prev) buf->bucket.prev->bucket.next = buf->bucket.next;
if (pool->hashtable[slot] == buf) pool->hashtable[slot] = buf->bucket.next;
buf->bucket.next = NULL;
buf->bucket.prev = NULL;
}
void
bufaddblk(struct bufblk *blk)
{
#if (BUFNEWHASH)
bufval_t val = bufmkhashkey(blk->dev, blk->num);
bufval_t key = bufhash(val);
struct bufblk *buf;
struct bufchain *chain = &bufhash[key];
#else
buval_t key = bufhash(blk->num);
long dkey = blk->dev & BUFDEVMASK;
struct bufblk *buf;
#endif
#if (BUFNEWHASH)
fmtxlk(&chain->lk);
buf = chain->list;
buf->tabprev = NULL;
if (buf) {
buf->tabprev = blk;
}
blk->tabnext = buf;
chain->list = buf;
fmtxunlk(&chain->lk);
#else
fmtxlk(&buflktab[dkey]);
buf = bufhash[dkey][key];
if (buf) {
buf->tabprev = blk;
}
bufhash[dkey][key] = blk;
fmtxunlk(&buflktab[dkey]);
#endif
return;
}
static struct buf *lookup_buffer(struct bufpool *pool, vfs_blkno_t blkno)
{
struct buf *buf;
buf = pool->hashtable[bufhash(blkno) % BUFPOOL_HASHSIZE];
while (buf && buf->blkno != blkno) buf = buf->bucket.next;
if (!buf) return NULL;
switch (buf->state)
{
case BUF_STATE_FREE:
panic("free buffer in cache");
break;
case BUF_STATE_CLEAN:
// Remove from clean list
if (buf->chain.next) buf->chain.next->chain.prev = buf->chain.prev;
if (buf->chain.prev) buf->chain.prev->chain.next = buf->chain.next;
if (pool->clean.head == buf) pool->clean.head = buf->chain.next;
if (pool->clean.tail == buf) pool->clean.tail = buf->chain.prev;
// Set state to locked and add lock
buf->chain.next = NULL;
buf->chain.prev = NULL;
buf->state = BUF_STATE_LOCKED;
buf->locks++;
break;
case BUF_STATE_DIRTY:
// Remove from dirty list
if (buf->chain.next) buf->chain.next->chain.prev = buf->chain.prev;
if (buf->chain.prev) buf->chain.prev->chain.next = buf->chain.next;
if (pool->dirty.head == buf) pool->dirty.head = buf->chain.next;
if (pool->dirty.tail == buf) pool->dirty.tail = buf->chain.prev;
// Set state to updated and add lock
buf->chain.next = NULL;
buf->chain.prev = NULL;
buf->state = BUF_STATE_UPDATED;
buf->locks++;
break;
case BUF_STATE_READING:
case BUF_STATE_WRITING:
// Wait for buffer to become ready. Buffer is locked by reader/writer
wait_for_buffer(buf);
break;
case BUF_STATE_LOCKED:
case BUF_STATE_UPDATED:
// Add lock
buf->locks++;
break;
case BUF_STATE_INVALID:
// Set state to locked, add lock and clear buffer
buf->state = BUF_STATE_LOCKED;
buf->locks++;
memset(buf->data, 0, pool->bufsize);
break;
default:
panic("invalid buffer state");
}
return buf;
}
