about Caching in Network File System

in article:Caching in Network File System,it says the caller must acquire the
FCB resource,in order to avoid deadlocks while calling the redirector, it must
be owned exclusive (using the ERESOURCE in the FCB itself).

There are two ERESOUCE in FCB header:
what is the ERESOURCE the article refer to?

Should I call FsRtlEnterFileSystem() ?
If I must ExAcquireResourceExclusive the PagingIoResource, should I do polling
(I think I don’t want to ExAcquireResourceExclusive the PagingIoResource,just
want to ExAcquireResourceExclusive the Resource).

And,I have known the IRP (not paging,not non-cached) may write through to the server.But,what about fastIO?
a FastIO also write to the server directly?I think not.