1 files changed, 173 insertions, 0 deletions
diff --git a/drivers/block/blkcache.c b/drivers/block/blkcache.c
new file mode 100644
index 0000000000..46a6059321
--- /dev/null
+++ b/drivers/block/blkcache.c
@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) Nelson Integration, LLC 2016
+ * Author: Eric Nelson<eric@nelint.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ */
+#include <config.h>
+#include <common.h>
+#include <malloc.h>
+#include <part.h>
+#include <linux/ctype.h>
+#include <linux/list.h>
+
+struct block_cache_node {
+	struct list_head lh;
+	int iftype;
+	int devnum;
+	lbaint_t start;
+	lbaint_t blkcnt;
+	unsigned long blksz;
+	char *cache;
+};
+
+static LIST_HEAD(block_cache);
+
+static struct block_cache_stats _stats = {
+	.max_blocks_per_entry = 2,
+	.max_entries = 32
+};
+
+static struct block_cache_node *cache_find(int iftype, int devnum,
+					   lbaint_t start, lbaint_t blkcnt,
+					   unsigned long blksz)
+{
+	struct block_cache_node *node;
+
+	list_for_each_entry(node, &block_cache, lh)
+		if ((node->iftype == iftype) &&
+		    (node->devnum == devnum) &&
+		    (node->blksz == blksz) &&
+		    (node->start <= start) &&
+		    (node->start + node->blkcnt >= start + blkcnt)) {
+			if (block_cache.next != &node->lh) {
+				/* maintain MRU ordering */
+				list_del(&node->lh);
+				list_add(&node->lh, &block_cache);
+			}
+			return node;
+		}
+	return 0;
+}
+
+int blkcache_read(int iftype, int devnum,
+		  lbaint_t start, lbaint_t blkcnt,
+		  unsigned long blksz, void *buffer)
+{
+	struct block_cache_node *node = cache_find(iftype, devnum, start,
+						   blkcnt, blksz);
+	if (node) {
+		const char *src = node->cache + (start - node->start) * blksz;
+		memcpy(buffer, src, blksz * blkcnt);
+		debug("hit: start " LBAF ", count " LBAFU "\n",
+		      start, blkcnt);
+		++_stats.hits;
+		return 1;
+	}
+
+	debug("miss: start " LBAF ", count " LBAFU "\n",
+	      start, blkcnt);
+	++_stats.misses;
+	return 0;
+}
+
+void blkcache_fill(int iftype, int devnum,
+		   lbaint_t start, lbaint_t blkcnt,
+		   unsigned long blksz, void const *buffer)
+{
+	lbaint_t bytes;
+	struct block_cache_node *node;
+
+	/* don't cache big stuff */
+	if (blkcnt > _stats.max_blocks_per_entry)
+		return;
+
+	if (_stats.max_entries == 0)
+		return;
+
+	bytes = blksz * blkcnt;
+	if (_stats.max_entries <= _stats.entries) {
+		/* pop LRU */
+		node = (struct block_cache_node *)block_cache.prev;
+		list_del(&node->lh);
+		_stats.entries--;
+		debug("drop: start " LBAF ", count " LBAFU "\n",
+		      node->start, node->blkcnt);
+		if (node->blkcnt * node->blksz < bytes) {
+			free(node->cache);
+			node->cache = 0;
+		}
+	} else {
+		node = malloc(sizeof(*node));
+		if (!node)
+			return;
+		node->cache = 0;
+	}
+
+	if (!node->cache) {
+		node->cache = malloc(bytes);
+		if (!node->cache) {
+			free(node);
+			return;
+		}
+	}
+
+	debug("fill: start " LBAF ", count " LBAFU "\n",
+	      start, blkcnt);
+
+	node->iftype = iftype;
+	node->devnum = devnum;
+	node->start = start;
+	node->blkcnt = blkcnt;
+	node->blksz = blksz;
+	memcpy(node->cache, buffer, bytes);
+	list_add(&node->lh, &block_cache);
+	_stats.entries++;
+}
+
+void blkcache_invalidate(int iftype, int devnum)
+{
+	struct list_head *entry, *n;
+	struct block_cache_node *node;
+
+	list_for_each_safe(entry, n, &block_cache) {
+		node = (struct block_cache_node *)entry;
+		if ((node->iftype == iftype) &&
+		    (node->devnum == devnum)) {
+			list_del(entry);
+			free(node->cache);
+			free(node);
+			--_stats.entries;
+		}
+	}
+}
+
+void blkcache_configure(unsigned blocks, unsigned entries)
+{
+	struct block_cache_node *node;
+	if ((blocks != _stats.max_blocks_per_entry) ||
+	    (entries != _stats.max_entries)) {
+		/* invalidate cache */
+		while (!list_empty(&block_cache)) {
+			node = (struct block_cache_node *)block_cache.next;
+			list_del(&node->lh);
+			free(node->cache);
+			free(node);
+		}
+		_stats.entries = 0;
+	}
+
+	_stats.max_blocks_per_entry = blocks;
+	_stats.max_entries = entries;
+
+	_stats.hits = 0;
+	_stats.misses = 0;
+}
+
+void blkcache_stats(struct block_cache_stats *stats)
+{
+	memcpy(stats, &_stats, sizeof(*stats));
+	_stats.hits = 0;
+	_stats.misses = 0;
+}