drm/mm: Fix search for smallest hole satisfying constraints

entry->size is the size of the node, not the size of the hole after it.
So the code would actually find the hole which can satisfy the
constraints and which is preceded by the smallest node, not the smallest
hole satisfying the constraints.
Reported-by: N"Huang, FrankR" <FrankR.Huang@amd.com>
Signed-off-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_mm.c

@@ -423,6 +423,8 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 
 	__drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
 			       flags & DRM_MM_SEARCH_BELOW) {
+		unsigned long hole_size = adj_end - adj_start;
+
 		if (mm->color_adjust) {
 			mm->color_adjust(entry, color, &adj_start, &adj_end);
 			if (adj_end <= adj_start)
@@ -435,9 +437,9 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 		if (!(flags & DRM_MM_SEARCH_BEST))
 			return entry;
 
-		if (entry->size < best_size) {
+		if (hole_size < best_size) {
 			best = entry;
-			best_size = entry->size;
+			best_size = hole_size;
 		}
 	}
 
@@ -465,6 +467,8 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
 
 	__drm_mm_for_each_hole(entry, mm, adj_start, adj_end,
 			       flags & DRM_MM_SEARCH_BELOW) {
+		unsigned long hole_size = adj_end - adj_start;
+
 		if (adj_start < start)
 			adj_start = start;
 		if (adj_end > end)
@@ -482,9 +486,9 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
 		if (!(flags & DRM_MM_SEARCH_BEST))
 			return entry;
 
-		if (entry->size < best_size) {
+		if (hole_size < best_size) {
 			best = entry;
-			best_size = entry->size;
+			best_size = hole_size;
 		}
 	}