[PATCH 02/33] drm/i915: Prefer list_first_entry_of_null

[Chris Wilson]

list_first_entry_or_null() can generate better code than using
if (!list_empty()) {ptr = list_first_entry()) ..., so put it to use.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c      | 12 +++++-------
 drivers/gpu/drm/i915/i915_gem_request.c  |  8 +++-----
 drivers/gpu/drm/i915/i915_gem_shrinker.c |  9 +++++----
 3 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 30da543e1bdf..38e7d992a20d 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2736,13 +2736,11 @@ static void i915_gtt_color_adjust(struct drm_mm_node *node,
 	if (node->color != color)
 		*start += 4096;
 
-	if (!list_empty(&node->node_list)) {
-		node = list_entry(node->node_list.next,
-				  struct drm_mm_node,
-				  node_list);
-		if (node->allocated && node->color != color)
-			*end -= 4096;
-	}
+	node = list_first_entry_or_null(&node->node_list,
+					struct drm_mm_node,
+					node_list);
+	if (node && node->allocated && node->color != color)
+		*end -= 4096;
 }
 
 static int i915_gem_setup_global_gtt(struct drm_device *dev,
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 60a3a343b3a8..49396b895a36 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -317,12 +317,10 @@ __i915_gem_request_alloc(struct intel_engine_cs *engine,
 		return ret;
 
 	/* Move the oldest request to the slab-cache (if not in use!) */
-	if (!list_empty(&engine->request_list)) {
-		req = list_first_entry(&engine->request_list,
+	req = list_first_entry_or_null(&engine->request_list,
 				       typeof(*req), list);
-		if (i915_gem_request_completed(req))
-			i915_gem_request_retire(req);
-	}
+	if (req && i915_gem_request_completed(req))
+		i915_gem_request_retire(req);
 
 	req = kmem_cache_zalloc(dev_priv->requests, GFP_KERNEL);
 	if (!req)
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index afaa2597e35e..9ffafdc02a30 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -163,17 +163,18 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 	 */
 	for (phase = phases; phase->list; phase++) {
 		struct list_head still_in_list;
+		struct drm_i915_gem_object *obj;
 
 		if ((flags & phase->bit) == 0)
 			continue;
 
 		INIT_LIST_HEAD(&still_in_list);
-		while (count < target && !list_empty(phase->list)) {
-			struct drm_i915_gem_object *obj;
+		while (count < target &&
+		       obj = list_first_entry_or_null(phase->list,
+						      typeof(*obj),
+						      global_list)) {
 			struct i915_vma *vma, *v;
 
-			obj = list_first_entry(phase->list,
-					       typeof(*obj), global_list);
 			list_move_tail(&obj->global_list, &still_in_list);
 
 			if (flags & I915_SHRINK_PURGEABLE &&
-- 
2.8.1