drm/msm: Fix wait_fence submitqueue leak

We weren't dropping the submitqueue reference in all paths.  In
particular, when the fence has already been signalled. Split out
a helper to simplify handling this in the various different return
paths.

Fixes: a61acbbe ("drm/msm: Track "seqno" fences by idr")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20211111192457.747899-2-robdclark@gmail.comSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_drv.c

@@ -967,29 +967,12 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
 	return ret;
 }
 
-static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
-		struct drm_file *file)
+static int wait_fence(struct msm_gpu_submitqueue *queue, uint32_t fence_id,
+		      ktime_t timeout)
 {
-	struct msm_drm_private *priv = dev->dev_private;
-	struct drm_msm_wait_fence *args = data;
-	ktime_t timeout = to_ktime(args->timeout);
-	struct msm_gpu_submitqueue *queue;
-	struct msm_gpu *gpu = priv->gpu;
 	struct dma_fence *fence;
 	int ret;
 
-	if (args->pad) {
-		DRM_ERROR("invalid pad: %08x\n", args->pad);
-		return -EINVAL;
-	}
-
-	if (!gpu)
-		return 0;
-
-	queue = msm_submitqueue_get(file->driver_priv, args->queueid);
-	if (!queue)
-		return -ENOENT;
-
 	/*
 	 * Map submitqueue scoped "seqno" (which is actually an idr key)
 	 * back to underlying dma-fence
@@ -1001,7 +984,7 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
 	ret = mutex_lock_interruptible(&queue->lock);
 	if (ret)
 		return ret;
-	fence = idr_find(&queue->fence_idr, args->fence);
+	fence = idr_find(&queue->fence_idr, fence_id);
 	if (fence)
 		fence = dma_fence_get_rcu(fence);
 	mutex_unlock(&queue->lock);
@@ -1017,6 +1000,32 @@ static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
 	}
 
 	dma_fence_put(fence);
+
+	return ret;
+}
+
+static int msm_ioctl_wait_fence(struct drm_device *dev, void *data,
+		struct drm_file *file)
+{
+	struct msm_drm_private *priv = dev->dev_private;
+	struct drm_msm_wait_fence *args = data;
+	struct msm_gpu_submitqueue *queue;
+	int ret;
+
+	if (args->pad) {
+		DRM_ERROR("invalid pad: %08x\n", args->pad);
+		return -EINVAL;
+	}
+
+	if (!priv->gpu)
+		return 0;
+
+	queue = msm_submitqueue_get(file->driver_priv, args->queueid);
+	if (!queue)
+		return -ENOENT;
+
+	ret = wait_fence(queue, args->fence, to_ktime(args->timeout));
+
 	msm_submitqueue_put(queue);
 
 	return ret;