[cache_writeback] Coded, needs testing

block-cache/mem_pool.cc

@@ -0,0 +1,57 @@
+#include "block-cache/mem_pool.h"
+
+#include <stdlib.h>
+
+using namespace bcache;
+using namespace boost;
+using namespace mempool_detail;
+
+#define PAGE_SIZE 4096
+
+//----------------------------------------------------------------
+
+mempool::mempool(size_t block_size, size_t total_mem)
+{
+	mem_ = alloc_aligned(total_mem, PAGE_SIZE);
+
+	unsigned nr_blocks = total_mem / block_size;
+	for (auto i = 0u; i < nr_blocks; i++)
+		free(static_cast<unsigned char *>(mem_) + (block_size * i));
+}
+
+mempool::~mempool()
+{
+	::free(mem_);
+}
+
+boost::optional<void *>
+mempool::alloc()
+{
+	if (free_.empty())
+		return optional<void *>();
+
+	mempool_detail::alloc_block &b = free_.front();
+	free_.pop_front();
+	return optional<void *>(reinterpret_cast<void *>(&b));
+}
+
+void
+mempool::free(void *data)
+{
+	mempool_detail::alloc_block *b = reinterpret_cast<mempool_detail::alloc_block *>(data);
+	free_.push_front(*b);
+}
+
+void *
+mempool::alloc_aligned(size_t len, size_t alignment)
+{
+	void *result = NULL;
+	int r = posix_memalign(&result, alignment, len);
+	if (r)
+		return NULL;
+
+	return result;
+}
+
+//----------------------------------------------------------------
+