Virtio-fs daemon expects fs_slave_io() returns the number of bytes
read/written on success, but we always return 0 and make userspace think
nothing has been read/written.
Fix it by returning the actual bytes read/written. Note that This
depends on the corresponding fix in vhost crate.
Fixes: #949
Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
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>
