ntdll WRITECOPY dropped from staging

Hello,

I noticed that the ntdll WRITECOPY changes got mostly dropped from staging in
commit https://github.com/wine-staging/wine-staging/commit/
16dce521242b3f4a52cd2c8799ce6fe464fac83c

> The current state even after multiple iterations, the whole
> WRITECOPY implemenet needs differently.  Upstream will need to
> do this.

As I understand it, the implementation marks WRITECOPY pages as read-only on
the unix side, handling the access violation and marking it as read-write
afterwards. (Correct me if I'm wrong)

What is wrong with the underlying concept, how should it be implemented
properly?

Regards,
Fabian Maurer