zlacker

I think the issue comes with trying to present a USB mass storage API to the host where you allow the host to write to any arbitrary byte offset of the mass storage device without the structure that is imposed by a file system.

If the host and guest both get presented with the same “array of bytes” mass storage interface, then they will compete and potentially mess up each other’s reads and writes, let’s say if they both treat that array of bytes as an ext4 file system and try to write a file system metadata to the same physical location at the same time.

Of course you have have a “virtual file system” exposed over USB, but isn’t that exactly what MTP is? The point is that USB mass storage is not a virtual file system.