Revert "weed volume: disable block cache on leveldb"

This reverts commit a55e708d36.

weed/filer2/leveldb/leveldb_store.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"github.com/syndtr/goleveldb/leveldb/opt"
 
 	"github.com/chrislusf/seaweedfs/weed/filer2"
 	"github.com/chrislusf/seaweedfs/weed/glog"
@@ -40,9 +39,7 @@ func (store *LevelDBStore) initialize(dir string) (err error) {
 		return fmt.Errorf("Check Level Folder %s Writable: %s", dir, err)
 	}
 
-	if store.db, err = leveldb.OpenFile(dir, &opt.Options{
-		BlockCacheCapacity: -1, // default value is 8MiB
-	}); err != nil {
+	if store.db, err = leveldb.OpenFile(dir, nil); err != nil {
 		glog.Infof("filer store open dir %s: %v", dir, err)
 		return
 	}