[PATCH] 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>
---
 drivers/gpu/drm/drm_mm.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index af93cc5..5d921e5 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -306,8 +306,8 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 {
 	struct drm_mm_node *entry;
 	struct drm_mm_node *best;
-	unsigned long adj_start;
-	unsigned long adj_end;
+	unsigned long hole_start;
+	unsigned long hole_end;
 	unsigned long best_size;
 
 	BUG_ON(mm->scanned_blocks);
@@ -315,7 +315,10 @@ static struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
 	best = NULL;
 	best_size = ~0UL;
 
-	drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
+	drm_mm_for_each_hole(entry, mm, hole_start, hole_end) {
+		unsigned long adj_start = hole_start;
+		unsigned long adj_end = hole_end;
+
 		if (mm->color_adjust) {
 			mm->color_adjust(entry, color, &adj_start, &adj_end);
 			if (adj_end <= adj_start)
@@ -328,9 +331,9 @@ 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_end - hole_start) < best_size) {
 			best = entry;
-			best_size = entry->size;
+			best_size = hole_end - hole_start;
 		}
 	}
 
@@ -341,14 +344,14 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
 							unsigned long size,
 							unsigned alignment,
 							unsigned long color,
-							unsigned long start,
-							unsigned long end,
+							unsigned long range_start,
+							unsigned long range_end,
 							enum drm_mm_search_flags flags)
 {
 	struct drm_mm_node *entry;
 	struct drm_mm_node *best;
-	unsigned long adj_start;
-	unsigned long adj_end;
+	unsigned long hole_start;
+	unsigned long hole_end;
 	unsigned long best_size;
 
 	BUG_ON(mm->scanned_blocks);
@@ -356,11 +359,9 @@ static struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_
 	best = NULL;
 	best_size = ~0UL;
 
-	drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
-		if (adj_start < start)
-			adj_start = start;
-		if (adj_end > end)
-			adj_end = end;
+	drm_mm_for_each_hole(entry, mm, hole_start, hole_end) {
+		unsigned long adj_start = max(hole_start, range_start);
+		unsigned long adj_end = min(hole_end, range_end);
 
 		if (mm->color_adjust) {
 			mm->color_adjust(entry, color, &adj_start, &adj_end);
@@ -374,9 +375,9 @@ 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_end - hole_start) < best_size) {
 			best = entry;
-			best_size = entry->size;
+			best_size = hole_end - hole_start;
 		}
 	}
 
-- 
1.9.0