mount: avoid use uint64 for greater than zero test

weed/filesys/file.go

@@ -108,10 +108,11 @@ func (file *File) Setattr(ctx context.Context, req *fuse.SetattrRequest, resp *f
 			// fmt.Printf("truncate %v \n", fullPath)
 			var chunks []*filer_pb.FileChunk
 			for _, chunk := range file.entry.Chunks {
-				if uint64(chunk.Offset)+chunk.Size > req.Size {
-					chunk.Size = req.Size - uint64(chunk.Offset)
+				int64Size := int64(chunk.Size)
+				if chunk.Offset+int64Size > int64(req.Size) {
+					int64Size = int64(req.Size) - chunk.Offset
 				}
-				if chunk.Size > 0 {
+				if int64Size > 0 {
 					chunks = append(chunks, chunk)
 				}
 			}