From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
This simplifies the code to not have so many one line functions and extra
logic. __mmu_notifier_register() simply becomes the entry point to
register the notifier, and the other one calls it under lock.
Also add a lockdep_assert to check that the callers are holding the lock
as expected.
Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>