* Brian Geffon:

Hi Florian,
copy_vma will make a copy of the existing VMA leaving the old VMA
unchanged, so the source keeps its existing protections, this is what
makes it very useful along with userfaultfd.

I see.  On the other hand, it's impossible to get the PROT_NONE behavior
by a subsequent mprotect call because the mremap has to fail in some
cases in vm.overcommit_memory=2 mode.  But maybe that other behavior can
be provided with a different flag if it turns out to be useful in the
future.

Thanks,
Florian