dma-buf: keep only not signaled fence in reservation_object_add_shared_replace v3

The amdgpu issue to also need signaled fences in the reservation objects
should be fixed by now.

Optimize the list by keeping only the not signaled yet fences around.

v2: temporary put the signaled fences at the end of the new container
v3: put the old fence at the end of the new container as well.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Tested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114142436.1360-1-christian.koenig@amd.com

drivers/dma-buf/reservation.c

@@ -145,8 +145,7 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
 				      struct reservation_object_list *fobj,
 				      struct dma_fence *fence)
 {
-	unsigned i;
-	struct dma_fence *old_fence = NULL;
+	unsigned i, j, k;
 
 	dma_fence_get(fence);
 
@@ -162,24 +161,21 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
 	 * references from the old struct are carried over to
 	 * the new.
 	 */
-	fobj->shared_count = old->shared_count;
-
-	for (i = 0; i < old->shared_count; ++i) {
+	for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
 		struct dma_fence *check;
 
 		check = rcu_dereference_protected(old->shared[i],
 						reservation_object_held(obj));
 
-		if (!old_fence && check->context == fence->context) {
-			old_fence = check;
-			RCU_INIT_POINTER(fobj->shared[i], fence);
-		} else
-			RCU_INIT_POINTER(fobj->shared[i], check);
-	}
-	if (!old_fence) {
-		RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
-		fobj->shared_count++;
+		if (check->context == fence->context ||
+		    dma_fence_is_signaled(check))
+			RCU_INIT_POINTER(fobj->shared[--k], check);
+		else
+			RCU_INIT_POINTER(fobj->shared[j++], check);
 	}
+	fobj->shared_count = j;
+	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
+	fobj->shared_count++;
 
 done:
 	preempt_disable();
@@ -192,10 +188,18 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
 	write_seqcount_end(&obj->seq);
 	preempt_enable();
 
-	if (old)
-		kfree_rcu(old, rcu);
+	if (!old)
+		return;
 
-	dma_fence_put(old_fence);
+	/* Drop the references to the signaled fences */
+	for (i = k; i < fobj->shared_max; ++i) {
+		struct dma_fence *f;
+
+		f = rcu_dereference_protected(fobj->shared[i],
+					      reservation_object_held(obj));
+		dma_fence_put(f);
+	}
+	kfree_rcu(old, rcu);
 }
 
 /**