[PATCH v2] drm/mm: Fix search for smallest hole satisfying constraints

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

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: "Huang, FrankR" <FrankR.Huang at amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---

v2: Less invasive fix.

 drivers/gpu/drm/drm_mm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index a2d45b74..8b16a10 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -392,6 +392,8 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 	best_size = ~0UL;
 
 	drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
+		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)
@@ -404,9 +406,9 @@ 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;
 		}
 	}
 
@@ -433,6 +435,8 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
 	best_size = ~0UL;
 
 	drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
+		unsigned long hole_size = adj_end - adj_start;
+
 		if (adj_start < start)
 			adj_start = start;
 		if (adj_end > end)
@@ -450,9 +454,9 @@ 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;
 		}
 	}
 
-- 
1.9.0