Merge branch 'inet-fix-defrag-units-dismantle-races'

Eric Dumazet says:

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inet: fix defrag units dismantle races

This series add a new pre_exit() method to struct pernet_operations
to solve a race in defrag units dismantle, without adding extra
delays to netns dismantles.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>