/*
* Handle a read request; fill in parts of the request that can
* be satisfied by the cache, use the supplied strategy routine to do
* device I/O and then use the I/O results to populate the cache.
*/
static int
read_strategy(void *devdata, int unit, int rw, daddr_t blk, size_t size,
char *buf, size_t *rsize)
{
struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
int p_size, result;
daddr_t p_blk, i, j, nblk;
caddr_t p_buf;
nblk = size / bcache_blksize;
result = 0;
/* Satisfy any cache hits up front */
for (i = 0; i < nblk; i++) {
if (bcache_lookup(buf + (bcache_blksize * i), blk + i)) {
bit_set(bcache_miss, i); /* cache miss */
bcache_misses++;
} else {
bit_clear(bcache_miss, i); /* cache hit */
bcache_hits++;
}
}
/* Go back and fill in any misses XXX optimise */
p_blk = -1;
p_buf = NULL;
p_size = 0;
for (i = 0; i < nblk; i++) {
if (bit_test(bcache_miss, i)) {
/* miss, add to pending transfer */
if (p_blk == -1) {
p_blk = blk + i;
p_buf = buf + (bcache_blksize * i);
p_size = 1;
} else {
p_size++;
}
} else if (p_blk != -1) {
/* hit, complete pending transfer */
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
if (result != 0)
goto done;
for (j = 0; j < p_size; j++)
bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
p_blk = -1;
}
}
if (p_blk != -1) {
/* pending transfer left */
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
if (result != 0)
goto done;
for (j = 0; j < p_size; j++)
bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
}
done:
if ((result == 0) && (rsize != NULL))
*rsize = size;
return(result);
}
/*
* Handle a transfer request; fill in parts of the request that can
* be satisfied by the cache, use the supplied strategy routine to do
* device I/O and then use the I/O results to populate the cache.
*
* Requests larger than 1/2 the cache size will be bypassed and go
* directly to the disk. XXX tune this.
*/
int
bcache_strategy(void *devdata, int rw, daddr_t blk, size_t size, void *buf, size_t *rsize)
{
struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
int nblk, p_size;
daddr_t p_blk;
caddr_t p_buf;
int i, j, result;
bcache_ops++;
/* bypass large requests, or when the cache is inactive */
if ((bcache_data == NULL) || ((size * 2 / bcache_blksize) > bcache_nblks)) {
DEBUG("bypass %d from %d", size / bcache_blksize, blk);
bcache_bypasses++;
return(dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
}
nblk = size / bcache_blksize;
result = 0;
/* Satisfy any cache hits up front */
for (i = 0; i < nblk; i++) {
if (bcache_lookup(buf + (bcache_blksize * i), blk + i)) {
bit_set(bcache_miss, i); /* cache miss */
bcache_misses++;
} else {
bit_clear(bcache_miss, i); /* cache hit */
bcache_hits++;
}
}
/* Go back and fill in any misses XXX optimise */
p_blk = -1;
p_buf = NULL;
p_size = 0;
for (i = 0; i < nblk; i++) {
if (bit_test(bcache_miss, i)) {
/* miss, add to pending transfer */
if (p_blk == -1) {
p_blk = blk + i;
p_buf = buf + (bcache_blksize * i);
p_size = 1;
} else {
p_size++;
}
} else if (p_blk != -1) {
/* hit, complete pending transfer */
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
if (result != 0)
goto done;
for (j = 0; j < p_size; j++)
bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
p_blk = -1;
}
}
if (p_blk != -1) {
/* pending transfer left */
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
if (result != 0)
goto done;
for (j = 0; j < p_size; j++)
bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
}
done:
if ((result == 0) && (rsize != NULL))
*rsize = size;
return(result);
}
