drm/i915: Preallocate the drm_mm_node prior to manipulating the GTT drm_mm manager

As we may reap neighbouring objects in order to free up pages for
allocations, we need to be careful not to allocate in the middle of the
drm_mm manager. To accomplish this, we can simply allocate the
drm_mm_node up front and then use the combined search & insert
drm_mm routines, reducing our code footprint in the process.

Fixes (partially) i-g-t/gem_tiled_swapping
Reported-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Again fixup atomic bikeshed.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -2890,7 +2890,7 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 {
 	struct drm_device *dev = obj->base.dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
-	struct drm_mm_node *free_space;
+	struct drm_mm_node *node;
 	u32 size, fence_size, fence_alignment, unfenced_alignment;
 	bool mappable, fenceable;
 	int ret;
@@ -2936,66 +2936,54 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 
 	i915_gem_object_pin_pages(obj);
 
+	node = kzalloc(sizeof(*node), GFP_KERNEL);
+	if (node == NULL) {
+		i915_gem_object_unpin_pages(obj);
+		return -ENOMEM;
+	}
+
  search_free:
 	if (map_and_fenceable)
-		free_space = drm_mm_search_free_in_range_color(&dev_priv->mm.gtt_space,
-							       size, alignment, obj->cache_level,
-							       0, dev_priv->mm.gtt_mappable_end,
-							       false);
+		ret = drm_mm_insert_node_in_range_generic(&dev_priv->mm.gtt_space, node,
+							  size, alignment, obj->cache_level,
+							  0, dev_priv->mm.gtt_mappable_end);
 	else
-		free_space = drm_mm_search_free_color(&dev_priv->mm.gtt_space,
-						      size, alignment, obj->cache_level,
-						      false);
-
-	if (free_space != NULL) {
-		if (map_and_fenceable)
-			free_space =
-				drm_mm_get_block_range_generic(free_space,
-							       size, alignment, obj->cache_level,
-							       0, dev_priv->mm.gtt_mappable_end,
-							       false);
-		else
-			free_space =
-				drm_mm_get_block_generic(free_space,
-							 size, alignment, obj->cache_level,
-							 false);
-	}
-	if (free_space == NULL) {
+		ret = drm_mm_insert_node_generic(&dev_priv->mm.gtt_space, node,
+						 size, alignment, obj->cache_level);
+	if (ret) {
 		ret = i915_gem_evict_something(dev, size, alignment,
 					       obj->cache_level,
 					       map_and_fenceable,
 					       nonblocking);
-		if (ret) {
-			i915_gem_object_unpin_pages(obj);
-			return ret;
-		}
+		if (ret == 0)
+			goto search_free;
 
-		goto search_free;
+		i915_gem_object_unpin_pages(obj);
+		kfree(node);
+		return ret;
 	}
-	if (WARN_ON(!i915_gem_valid_gtt_space(dev,
-					      free_space,
-					      obj->cache_level))) {
+	if (WARN_ON(!i915_gem_valid_gtt_space(dev, node, obj->cache_level))) {
 		i915_gem_object_unpin_pages(obj);
-		drm_mm_put_block(free_space);
+		drm_mm_put_block(node);
 		return -EINVAL;
 	}
 
 	ret = i915_gem_gtt_prepare_object(obj);
 	if (ret) {
 		i915_gem_object_unpin_pages(obj);
-		drm_mm_put_block(free_space);
+		drm_mm_put_block(node);
 		return ret;
 	}
 
 	list_move_tail(&obj->gtt_list, &dev_priv->mm.bound_list);
 	list_add_tail(&obj->mm_list, &dev_priv->mm.inactive_list);
 
-	obj->gtt_space = free_space;
-	obj->gtt_offset = free_space->start;
+	obj->gtt_space = node;
+	obj->gtt_offset = node->start;
 
 	fenceable =
-		free_space->size == fence_size &&
-		(free_space->start & (fence_alignment - 1)) == 0;
+		node->size == fence_size &&
+		(node->start & (fence_alignment - 1)) == 0;
 
 	mappable =
 		obj->gtt_offset + obj->base.size <= dev_priv->mm.gtt_mappable_end;