Re: [PATCH v2] mm: Add MREMAP_DONTUNMAP to mremap().

[Florian Weimer]

* Brian Geffon:

> When remapping an anonymous, private mapping, if MREMAP_DONTUNMAP is
> set, the source mapping will not be removed. Instead it will be
> cleared as if a brand new anonymous, private mapping had been created
> atomically as part of the mremap() call.  If a userfaultfd was watching
> the source, it will continue to watch the new mapping.  For a mapping
> that is shared or not anonymous, MREMAP_DONTUNMAP will cause the
> mremap() call to fail. MREMAP_DONTUNMAP implies that MREMAP_FIXED is
> also used. The final result is two equally sized VMAs where the
> destination contains the PTEs of the source.

What will be the protection flags of the source mapping?  Will they
remain unchanged?  Or PROT_NONE?

Thanks,
Florian