Re: [RFC v3 PATCH 4/5] mm: mmap: zap pages with read mmap_sem for large mapping

[Michal Hocko]

On Fri 29-06-18 20:15:47, Andrew Morton wrote:
[...]
> Would one of your earlier designs have addressed all usecases?  I
> expect the dumb unmap-a-little-bit-at-a-time approach would have?

It has been already pointed out that this will not work. You simply
cannot drop the mmap_sem during unmap because another thread could
change the address space under your feet. So you need some form of
VM_DEAD and handle concurrent and conflicting address space operations.
-- 
Michal Hocko
SUSE Labs