[block_manager] Hard code block size to 4k.

We're never going to use anything other than 4k, and by hard coding it we
avoid making block_manager a template.

block-cache/block_cache.cc

@@ -19,10 +19,6 @@ using namespace file_utils;
 
 //----------------------------------------------------------------
 
-// FIXME: get from linux headers
-#define SECTOR_SHIFT 9
-#define PAGE_SIZE 4096
-
 #define MIN_BLOCKS 16
 #define WRITEBACK_LOW_THRESHOLD_PERCENT 33
 #define WRITEBACK_HIGH_THRESHOLD_PERCENT 66

block-cache/block_cache.h

@@ -3,6 +3,7 @@
 
 #include "base/container_of.h"
 #include "base/file_utils.h"
+#include "block-cache/io_engine.h"
 
 #include <boost/intrusive/list.hpp>
 #include <boost/intrusive/set.hpp>