Apple released with iOS 10.3, and the new file system with APFS file system. This API did not return any error, but it seems iOS did not reserve the space for me, because after the API is called, I check the available space in my iPhone, it seems the storage space is still there, iOS did not create this file really.
So the question will be in iOS 10.3, is there any similar API I can used to reserve a big storage quickly.