blob: 8ac5a49170cfc2691176d9e6601addd604bc5794 [file] [log] [blame]
/*
* Copyright (c) 2007 Travis Geiselbrecht
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <list.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <debug.h>
#include <lib/bcache.h>
#include <lib/bio.h>
#define LOCAL_TRACE 0
struct bcache_block {
struct list_node node;
bnum_t blocknum;
int ref_count;
bool is_dirty;
void *ptr;
};
struct bcache_stats {
uint32_t hits;
uint32_t depth;
uint32_t misses;
uint32_t reads;
uint32_t writes;
};
struct bcache {
bdev_t *dev;
size_t block_size;
int count;
struct bcache_stats stats;
struct list_node free_list;
struct list_node lru_list;
struct bcache_block *blocks;
};
bcache_t bcache_create(bdev_t *dev, size_t block_size, int block_count)
{
struct bcache *cache;
cache = malloc(sizeof(struct bcache));
cache->dev = dev;
cache->block_size = block_size;
cache->count = block_count;
memset(&cache->stats, 0, sizeof(cache->stats));
list_initialize(&cache->free_list);
list_initialize(&cache->lru_list);
cache->blocks = malloc(sizeof(struct bcache_block) * block_count);
int i;
for (i=0; i < block_count; i++) {
cache->blocks[i].ref_count = 0;
cache->blocks[i].is_dirty = false;
cache->blocks[i].ptr = malloc(block_size);
// add to the free list
list_add_head(&cache->free_list, &cache->blocks[i].node);
}
return (bcache_t)cache;
}
static int flush_block(struct bcache *cache, struct bcache_block *block)
{
int rc;
rc = bio_write(cache->dev, block->ptr,
(off_t)block->blocknum * cache->block_size,
cache->block_size);
if (rc < 0)
goto exit;
block->is_dirty = false;
cache->stats.writes++;
rc = 0;
exit:
return (rc);
}
void bcache_destroy(bcache_t _cache)
{
struct bcache *cache = _cache;
int i;
for (i=0; i < cache->count; i++) {
DEBUG_ASSERT(cache->blocks[i].ref_count == 0);
if (cache->blocks[i].is_dirty)
printf("warning: freeing dirty block %u\n",
cache->blocks[i].blocknum);
free(cache->blocks[i].ptr);
}
free(cache);
}
/* find a block if it's already present */
static struct bcache_block *find_block(struct bcache *cache, uint blocknum)
{
uint32_t depth = 0;
struct bcache_block *block;
LTRACEF("num %u\n", blocknum);
block = NULL;
list_for_every_entry(&cache->lru_list, block, struct bcache_block, node) {
LTRACEF("looking at entry %p, num %u\n", block, block->blocknum);
depth++;
if (block->blocknum == blocknum) {
list_delete(&block->node);
list_add_tail(&cache->lru_list, &block->node);
cache->stats.hits++;
cache->stats.depth += depth;
return block;
}
}
cache->stats.misses++;
return NULL;
}
/* allocate a new block */
static struct bcache_block *alloc_block(struct bcache *cache)
{
int err;
struct bcache_block *block;
/* pop one off the free list if it's present */
block = list_remove_head_type(&cache->free_list, struct bcache_block, node);
if (block) {
block->ref_count = 0;
list_add_tail(&cache->lru_list, &block->node);
LTRACEF("found block %p on free list\n", block);
return block;
}
/* walk the lru, looking for a free block */
list_for_every_entry(&cache->lru_list, block, struct bcache_block, node) {
LTRACEF("looking at %p, num %u\n", block, block->blocknum);
if (block->ref_count == 0) {
if (block->is_dirty) {
err = flush_block(cache, block);
if (err)
return NULL;
}
// add it to the tail of the lru
list_delete(&block->node);
list_add_tail(&cache->lru_list, &block->node);
return block;
}
}
return NULL;
}
static struct bcache_block *find_or_fill_block(struct bcache *cache, uint blocknum)
{
int err;
LTRACEF("block %u\n", blocknum);
/* see if it's already in the cache */
struct bcache_block *block = find_block(cache, blocknum);
if (block == NULL) {
LTRACEF("wasn't allocated\n");
/* allocate a new block and fill it */
block = alloc_block(cache);
DEBUG_ASSERT(block);
LTRACEF("wasn't allocated, new block %p\n", block);
block->blocknum = blocknum;
err = bio_read(cache->dev, block->ptr, (off_t)blocknum * cache->block_size, cache->block_size);
if (err < 0) {
/* free the block, return an error */
list_add_tail(&cache->free_list, &block->node);
return NULL;
}
cache->stats.reads++;
}
DEBUG_ASSERT(block->blocknum == blocknum);
return block;
}
int bcache_read_block(bcache_t _cache, void *buf, uint blocknum)
{
struct bcache *cache = _cache;
LTRACEF("buf %p, blocknum %u\n", buf, blocknum);
struct bcache_block *block = find_or_fill_block(cache, blocknum);
if (block == NULL) {
/* error */
return -1;
}
memcpy(buf, block->ptr, cache->block_size);
return 0;
}
int bcache_get_block(bcache_t _cache, void **ptr, uint blocknum)
{
struct bcache *cache = _cache;
LTRACEF("ptr %p, blocknum %u\n", ptr, blocknum);
DEBUG_ASSERT(ptr);
struct bcache_block *block = find_or_fill_block(cache, blocknum);
if (block == NULL) {
/* error */
return -1;
}
/* increment the ref count to keep it from being freed */
block->ref_count++;
*ptr = block->ptr;
return 0;
}
int bcache_put_block(bcache_t _cache, uint blocknum)
{
struct bcache *cache = _cache;
LTRACEF("blocknum %u\n", blocknum);
struct bcache_block *block = find_block(cache, blocknum);
/* be pretty hard on the caller for now */
DEBUG_ASSERT(block);
DEBUG_ASSERT(block->ref_count > 0);
block->ref_count--;
return 0;
}
int bcache_mark_block_dirty(bcache_t priv, uint blocknum)
{
int err;
struct bcache *cache = priv;
struct bcache_block *block;
block = find_block(cache, blocknum);
if (!block) {
err = -1;
goto exit;
}
block->is_dirty = true;
err = 0;
exit:
return (err);
}
int bcache_zero_block(bcache_t priv, uint blocknum)
{
int err;
struct bcache *cache = priv;
struct bcache_block *block;
block = find_block(cache, blocknum);
if (!block) {
block = alloc_block(cache);
if (!block) {
err = -1;
goto exit;
}
block->blocknum = blocknum;
}
memset(block->ptr, 0, cache->block_size);
block->is_dirty = true;
err = 0;
exit:
return (err);
}
int bcache_flush(bcache_t priv)
{
int err;
struct bcache *cache = priv;
struct bcache_block *block;
list_for_every_entry(&cache->lru_list, block, struct bcache_block, node) {
if (block->is_dirty) {
err = flush_block(cache, block);
if (err)
goto exit;
}
}
err = 0;
exit:
return (err);
}
void bcache_dump(bcache_t priv, const char *name)
{
uint32_t finds;
struct bcache *cache = priv;
finds = cache->stats.hits + cache->stats.misses;
printf("%s: hits=%u(%u%%) depth=%u misses=%u(%u%%) reads=%u writes=%u\n",
name,
cache->stats.hits,
finds ? (cache->stats.hits * 100) / finds : 0,
cache->stats.hits ? cache->stats.depth / cache->stats.hits : 0,
cache->stats.misses,
finds ? (cache->stats.misses * 100) / finds : 0,
cache->stats.reads,
cache->stats.writes);
}