Re: [PATCH v2 2/5] userfaultfd: non-cooperative: add event for memory unmaps

[Michal Hocko]

On Fri 27-01-17 20:44:30, Mike Rapoport wrote:
> When a non-cooperative userfaultfd monitor copies pages in the background,
> it may encounter regions that were already unmapped. Addition of
> UFFD_EVENT_UNMAP allows the uffd monitor to track precisely changes in the
> virtual memory layout.
> 
> Since there might be different uffd contexts for the affected VMAs, we
> first should create a temporary representation for the unmap event for each
> uffd context and then notify them one by one to the appropriate userfault
> file descriptors.
> 
> The event notification occurs after the mmap_sem has been released.
> 
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>

This breaks NOMMU compilation
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