[lib][bcache] add a simple block device cache

include/lib/bcache.h

@@ -0,0 +1,40 @@
+/*
+ * 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.
+ */
+#ifndef __LIB_BCACHE_H
+#define __LIB_BCACHE_H
+
+#include <lib/bio.h>
+
+typedef void * bcache_t;
+
+bcache_t bcache_create(bdev_t *dev, size_t block_size, int block_count);
+void bcache_destroy(bcache_t);
+
+int bcache_read_block(bcache_t, void *, uint block);
+
+// get and put a pointer directly to the block
+int bcache_get_block(bcache_t, void **, uint block);
+int bcache_put_block(bcache_t, uint block);
+
+#endif
+

lib/bcache/bcache.c

@@ -0,0 +1,348 @@
+/*
+ * 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);
+}

lib/bcache/rules.mk

@@ -0,0 +1,6 @@
+LOCAL_DIR := $(GET_LOCAL_DIR)
+
+MODULES += lib/bio
+
+OBJS += \
+	$(LOCAL_DIR)/bcache.o