[PATCH] dma-buf: make dma_fence structure a bit smaller

[Chris Wilson]

Quoting Christian König (2019-08-07 14:54:05)
> The ruc and cb_list are never used at the same time.
> This smal change is actually making the structure 16% smaller.
(Trivial pair of typos)

Yes. We clear the callback list on kref_put so that by the time we
release the fence it is unused. No one should be adding to the cb_list
that they don't themselves hold a reference for, this only now makes for
a much more spectacular use-after-free. :)

> Signed-off-by: Christian König <christian.koenig at amd.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris