This introduces setupmapping and removemapping methods to server.rs,
passthrough.rs and filesystem.rs in order to support virtiofs dax mode
inside guest.
Since we don't really want the server.rs to know that it is dealing with
vhost-user specifically, this is making it more generic by adding a new
trait which has three functions map()/unmap()/sync() corresponding to
fs_slave_{map, unmap, sync}, server.rs will take anything that implements
the trait.
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Add the `Filesystem` trait, which is the main interface between the
transport and the actual file system implementation.
This code has been ported over from crosvm commit
961461350c0b6824e5f20655031bf6c6bf6b7c30.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
