[PATCH] drm: Only evict the blocks required to create the requested hole

[Chris Wilson]

Avoid clobbering adjacent blocks if they happen to expire earlier and
amalgamate together to form the requested hole.

In passing this fixes a regression from
commit ea7b1dd44867e9cd6bac67e7c9fc3f128b5b255c
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Fri Feb 18 17:59:12 2011 +0100

    drm: mm: track free areas implicitly

which swaps the end address for size (with a potential overflow) and
effectively causes the eviction code to clobber almost all earlier
buffers above the evictee.

v2: Check the original hole not the adjusted as the coloring may confuse
us when later searching for the overlapping nodes. Also make sure that
we do apply the range restriction and color adjustment in the same
order for both scanning, searching and insertion.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/drm_mm.c |   45 +++++++++++++++++----------------------------
 include/drm/drm_mm.h     |    2 +-
 2 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index b751b8e..5847669 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -244,11 +244,13 @@ static void drm_mm_insert_helper_range(struct drm_mm_node *hole_node,
 
 	BUG_ON(!hole_node->hole_follows || node->allocated);
 
-	if (mm->color_adjust)
-		mm->color_adjust(hole_node, color, &adj_start, &adj_end);
-
 	if (adj_start < start)
 		adj_start = start;
+	if (adj_end > end)
+		adj_end = end;
+
+	if (mm->color_adjust)
+		mm->color_adjust(hole_node, color, &adj_start, &adj_end);
 
 	if (alignment) {
 		unsigned tmp = adj_start % alignment;
@@ -519,7 +521,7 @@ void drm_mm_init_scan(struct drm_mm *mm,
 	mm->scan_size = size;
 	mm->scanned_blocks = 0;
 	mm->scan_hit_start = 0;
-	mm->scan_hit_size = 0;
+	mm->scan_hit_end = 0;
 	mm->scan_check_range = 0;
 	mm->prev_scanned_node = NULL;
 }
@@ -546,7 +548,7 @@ void drm_mm_init_scan_with_range(struct drm_mm *mm,
 	mm->scan_size = size;
 	mm->scanned_blocks = 0;
 	mm->scan_hit_start = 0;
-	mm->scan_hit_size = 0;
+	mm->scan_hit_end = 0;
 	mm->scan_start = start;
 	mm->scan_end = end;
 	mm->scan_check_range = 1;
@@ -565,8 +567,7 @@ int drm_mm_scan_add_block(struct drm_mm_node *node)
 	struct drm_mm *mm = node->mm;
 	struct drm_mm_node *prev_node;
 	unsigned long hole_start, hole_end;
-	unsigned long adj_start;
-	unsigned long adj_end;
+	unsigned long adj_start, adj_end;
 
 	mm->scanned_blocks++;
 
@@ -583,14 +584,8 @@ int drm_mm_scan_add_block(struct drm_mm_node *node)
 	node->node_list.next = &mm->prev_scanned_node->node_list;
 	mm->prev_scanned_node = node;
 
-	hole_start = drm_mm_hole_node_start(prev_node);
-	hole_end = drm_mm_hole_node_end(prev_node);
-
-	adj_start = hole_start;
-	adj_end = hole_end;
-
-	if (mm->color_adjust)
-		mm->color_adjust(prev_node, mm->scan_color, &adj_start, &adj_end);
+	adj_start = hole_start = drm_mm_hole_node_start(prev_node);
+	adji_end = hole_end = drm_mm_hole_node_end(prev_node);
 
 	if (mm->scan_check_range) {
 		if (adj_start < mm->scan_start)
@@ -599,11 +594,14 @@ int drm_mm_scan_add_block(struct drm_mm_node *node)
 			adj_end = mm->scan_end;
 	}
 
+	if (mm->color_adjust)
+		mm->color_adjust(prev_node, mm->scan_color,
+				 adj_start, adj_end);
+
 	if (check_free_hole(adj_start, adj_end,
 			    mm->scan_size, mm->scan_alignment)) {
 		mm->scan_hit_start = hole_start;
-		mm->scan_hit_size = hole_end;
-
+		mm->scan_hit_end = hole_end;
 		return 1;
 	}
 
@@ -639,19 +637,10 @@ int drm_mm_scan_remove_block(struct drm_mm_node *node)
 			       node_list);
 
 	prev_node->hole_follows = node->scanned_preceeds_hole;
-	INIT_LIST_HEAD(&node->node_list);
 	list_add(&node->node_list, &prev_node->node_list);
 
-	/* Only need to check for containement because start&size for the
-	 * complete resulting free block (not just the desired part) is
-	 * stored. */
-	if (node->start >= mm->scan_hit_start &&
-	    node->start + node->size
-	    		<= mm->scan_hit_start + mm->scan_hit_size) {
-		return 1;
-	}
-
-	return 0;
+	 return (__drm_mm_hole_node_end(node) > mm->scan_hit_start &&
+		 node->start < mm->scan_hit_end);
 }
 EXPORT_SYMBOL(drm_mm_scan_remove_block);
 
diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
index cd45365..58b8979 100644
--- a/include/drm/drm_mm.h
+++ b/include/drm/drm_mm.h
@@ -70,7 +70,7 @@ struct drm_mm {
 	unsigned long scan_color;
 	unsigned long scan_size;
 	unsigned long scan_hit_start;
-	unsigned scan_hit_size;
+	unsigned long scan_hit_end;
 	unsigned scanned_blocks;
 	unsigned long scan_start;
 	unsigned long scan_end;
-- 
1.7.10.4