Here’s an interesting datapoint:
(At least in Win7) luafv.sys returns FLT_PREOP_DISALLOW_FASTIO
unconditionally for IRP_MJ_NETWORK_QUERY_OPEN.
kd> uf luafv!LuafvPreNetworkQueryOpen
luafv!LuafvPreNetworkQueryOpen:
8e473a9e 6a03 push 3
8e473aa0 58 pop eax
8e473aa1 c20c00 ret 0Ch
There is a very common meme that states that the only FastIO operation worth
implementing is IRP_MJ_NETWORK_QUERY_OPEN. It now seems that it isn’t even
worth implementing that one.