dma-buf: add some lockdep asserts to the reservation object implementation

This adds lockdep asserts to the reservation functions which state in their
documentation that obj->lock must be held. Allows builds with PROVE_LOCKING
enabled to check that the locking requirements are met.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180111165302.25556-1-l.stach@pengutronix.de

drivers/dma-buf/reservation.c

@@ -73,6 +73,8 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
 	struct reservation_object_list *old, *new;
 	unsigned int i, j, k, max;
 
+	reservation_object_assert_held(obj);
+
 	old = reservation_object_get_list(obj);
 
 	if (old && old->shared_max) {
@@ -151,6 +153,8 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
 
 	dma_fence_get(fence);
 
+	reservation_object_assert_held(obj);
+
 	fobj = reservation_object_get_list(obj);
 	count = fobj->shared_count;
 
@@ -196,6 +200,8 @@ void reservation_object_add_excl_fence(struct reservation_object *obj,
 	struct reservation_object_list *old;
 	u32 i = 0;
 
+	reservation_object_assert_held(obj);
+
 	old = reservation_object_get_list(obj);
 	if (old)
 		i = old->shared_count;
@@ -236,6 +242,8 @@ int reservation_object_copy_fences(struct reservation_object *dst,
 	size_t size;
 	unsigned i;
 
+	reservation_object_assert_held(dst);
+
 	rcu_read_lock();
 	src_list = rcu_dereference(src->fence);