[PATCH 4/4] mm, notifier: Catch sleeping/blocking for !blockable

[Jason Gunthorpe]

On Thu, Aug 22, 2019 at 10:42:39AM +0200, Daniel Vetter wrote:

> > RDMA has a mutex:
> >
> > ib_umem_notifier_invalidate_range_end
> >   rbt_ib_umem_for_each_in_range
> >    invalidate_range_start_trampoline
> >     ib_umem_notifier_end_account
> >       mutex_lock(&umem_odp->umem_mutex);
> >
> > I'm working to delete this path though!
> >
> > nonblocking or not follows the start, the same flag gets placed into
> > the mmu_notifier_range struct passed to end.
> 
> Ok, makes sense.
> 
> I guess that also means the might_sleep (I started on that) in
> invalidate_range_end also needs to be conditional? Or not bother with
> a might_sleep in invalidate_range_end since you're working on removing
> the last sleep in there?

I might suggest the same pattern as used for locked, the might_sleep
unconditionally on the start, and a 2nd might sleep after the IF in
__mmu_notifier_invalidate_range_end()

Observing that by audit all the callers already have the same locking
context for start/end

Jason