[PATCH v5 3/3] drm/buddy: Add defragmentation support

[Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>]

Add a function to support defragmentation.

v5: Defragment the freelist order array beginning
    from min_order.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
Suggested-by: Matthew Auld <matthew.auld@xxxxxxxxx>
---
 drivers/gpu/drm/drm_buddy.c | 70 ++++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index d44172f23f05..8aa6d31cb826 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -276,10 +276,12 @@ drm_get_buddy(struct drm_buddy_block *block)
 }
 EXPORT_SYMBOL(drm_get_buddy);
 
-static void __drm_buddy_free(struct drm_buddy *mm,
-			     struct drm_buddy_block *block)
+static unsigned int __drm_buddy_free(struct drm_buddy *mm,
+				     struct drm_buddy_block *block,
+				     bool defrag)
 {
 	struct drm_buddy_block *parent;
+	unsigned int order;
 
 	while ((parent = block->parent)) {
 		struct drm_buddy_block *buddy;
@@ -289,12 +291,14 @@ static void __drm_buddy_free(struct drm_buddy *mm,
 		if (!drm_buddy_block_is_free(buddy))
 			break;
 
-		if (drm_buddy_block_is_clear(block) !=
-		    drm_buddy_block_is_clear(buddy))
-			break;
+		if (!defrag) {
+			if (drm_buddy_block_is_clear(block) !=
+			    drm_buddy_block_is_clear(buddy))
+				break;
 
-		if (drm_buddy_block_is_clear(block))
-			mark_cleared(parent);
+			if (drm_buddy_block_is_clear(block))
+				mark_cleared(parent);
+		}
 
 		list_del(&buddy->link);
 
@@ -304,7 +308,37 @@ static void __drm_buddy_free(struct drm_buddy *mm,
 		block = parent;
 	}
 
+	order = drm_buddy_block_order(block);
 	mark_free(mm, block);
+
+	return order;
+}
+
+static void drm_buddy_defrag(struct drm_buddy *mm,
+			     unsigned int min_order)
+{
+	struct drm_buddy_block *block;
+	struct list_head *list;
+	unsigned int order;
+	int i;
+
+	if (min_order > mm->max_order)
+		return;
+
+	for (i = min_order - 1; i >= 0; i--) {
+		list = &mm->free_list[i];
+		if (list_empty(list))
+			continue;
+
+		list_for_each_entry_reverse(block, list, link) {
+			if (!block->parent)
+				continue;
+
+			order = __drm_buddy_free(mm, block, 1);
+			if (order >= min_order)
+				return;
+		}
+	}
 }
 
 /**
@@ -321,7 +355,7 @@ void drm_buddy_free_block(struct drm_buddy *mm,
 	if (drm_buddy_block_is_clear(block))
 		mm->clear_avail += drm_buddy_block_size(mm, block);
 
-	__drm_buddy_free(mm, block);
+	__drm_buddy_free(mm, block, 0);
 }
 EXPORT_SYMBOL(drm_buddy_free_block);
 
@@ -447,7 +481,7 @@ __alloc_range_bias(struct drm_buddy *mm,
 	if (buddy &&
 	    (drm_buddy_block_is_free(block) &&
 	     drm_buddy_block_is_free(buddy)))
-		__drm_buddy_free(mm, block);
+		__drm_buddy_free(mm, block, 0);
 	return ERR_PTR(err);
 }
 
@@ -577,7 +611,7 @@ alloc_from_freelist(struct drm_buddy *mm,
 
 err_undo:
 	if (tmp != order)
-		__drm_buddy_free(mm, block);
+		__drm_buddy_free(mm, block, 0);
 	return ERR_PTR(err);
 }
 
@@ -657,7 +691,7 @@ static int __alloc_range(struct drm_buddy *mm,
 	if (buddy &&
 	    (drm_buddy_block_is_free(block) &&
 	     drm_buddy_block_is_free(buddy)))
-		__drm_buddy_free(mm, block);
+		__drm_buddy_free(mm, block, 0);
 
 err_free:
 	if (err == -ENOSPC && total_allocated_on_err) {
@@ -903,7 +937,17 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
 
 			if (order-- == min_order) {
 				if (flags & DRM_BUDDY_CONTIGUOUS_ALLOCATION &&
-				    !(flags & DRM_BUDDY_RANGE_ALLOCATION))
+				    !(flags & DRM_BUDDY_RANGE_ALLOCATION)) {
+					/*
+					 * Defragment the freelist
+					 */
+					drm_buddy_defrag(mm, min_order);
+					/*
+					 * Try contiguous block allocation again!
+					 */
+					block = alloc_from_freelist(mm, min_order, flags);
+					if (!IS_ERR(block))
+						break;
 					/*
 					 * Try contiguous block allocation through
 					 * try harder method
@@ -912,6 +956,8 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
 									 original_size,
 									 original_min_size,
 									 blocks);
+				}
+
 				err = -ENOSPC;
 				goto err_free;
 			}
-- 
2.25.1