Is there any file system that can be mounted multiple times and supports concurrent file access for Linux? Basically I want something like a cluster file system but without the need to have a running network for a distributed lock manager. That can be very handy in connection with virtual machines that can share data with the host or another VM without the need to create a network link. This I want to avoid to keep the network architecture secure (virtual machine in DMZ) but share large files. No need to scale it up, just two machines that mount the same block device.

Shouldn't it be possible to have file locking information right on the disk?