multiple fixes

* adjust isOpen count
* move ContinuousDirtyPages lock to filehandle
* fix problem with MergeIntoVisibles, avoid reusing slices
* let filer delete the garbage

weed/filesys/meta_cache/meta_cache.go

@@ -50,6 +50,10 @@ func openMetaStore(dbFolder string) filer2.FilerStore {
 func (mc *MetaCache) InsertEntry(ctx context.Context, entry *filer2.Entry) error {
 	mc.Lock()
 	defer mc.Unlock()
+	return mc.doInsertEntry(ctx, entry)
+}
+
+func (mc *MetaCache) doInsertEntry(ctx context.Context, entry *filer2.Entry) error {
 	filer_pb.BeforeEntrySerialization(entry.Chunks)
 	return mc.actualStore.InsertEntry(ctx, entry)
 }

weed/filesys/meta_cache/meta_cache_init.go

@@ -18,7 +18,7 @@ func EnsureVisited(mc *MetaCache, client filer_pb.FilerClient, dirPath util.Full
 
 		err = filer_pb.ReadDirAllEntries(client, dirPath, "", func(pbEntry *filer_pb.Entry, isLast bool) error {
 			entry := filer2.FromPbEntry(string(dirPath), pbEntry)
-			if err := mc.InsertEntry(context.Background(), entry); err != nil {
+			if err := mc.doInsertEntry(context.Background(), entry); err != nil {
 				glog.V(0).Infof("read %s: %v", entry.FullPath, err)
 				return err
 			}