drm/vmwgfx: Use an RBtree instead of linked list for MOB resources

With emulated coherent memory we need to be able to quickly look up
a resource from the MOB offset. Instead of traversing a linked list with
O(n) worst case, use an RBtree with O(log n) worst case complexity.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_bo.c

@@ -463,6 +463,7 @@ void vmw_bo_bo_free(struct ttm_buffer_object *bo)
 	struct vmw_buffer_object *vmw_bo = vmw_buffer_object(bo);
 
 	WARN_ON(vmw_bo->dirty);
+	WARN_ON(!RB_EMPTY_ROOT(&vmw_bo->res_tree));
 	vmw_bo_unmap(vmw_bo);
 	kfree(vmw_bo);
 }
@@ -479,6 +480,7 @@ static void vmw_user_bo_destroy(struct ttm_buffer_object *bo)
 	struct vmw_buffer_object *vbo = &vmw_user_bo->vbo;
 
 	WARN_ON(vbo->dirty);
+	WARN_ON(!RB_EMPTY_ROOT(&vbo->res_tree));
 	vmw_bo_unmap(vbo);
 	ttm_prime_object_kfree(vmw_user_bo, prime);
 }
@@ -514,8 +516,7 @@ int vmw_bo_init(struct vmw_private *dev_priv,
 	memset(vmw_bo, 0, sizeof(*vmw_bo));
 	BUILD_BUG_ON(TTM_MAX_BO_PRIORITY <= 3);
 	vmw_bo->base.priority = 3;
-
-	INIT_LIST_HEAD(&vmw_bo->res_list);
+	vmw_bo->res_tree = RB_ROOT;
 
 	ret = ttm_bo_init(bdev, &vmw_bo->base, size,
 			  ttm_bo_type_device, placement,

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -100,7 +100,7 @@ struct vmw_fpriv {
 /**
  * struct vmw_buffer_object - TTM buffer object with vmwgfx additions
  * @base: The TTM buffer object
- * @res_list: List of resources using this buffer object as a backing MOB
+ * @res_tree: RB tree of resources using this buffer object as a backing MOB
  * @pin_count: pin depth
  * @cpu_writers: Number of synccpu write grabs. Protected by reservation when
  * increased. May be decreased without reservation.
@@ -111,7 +111,7 @@ struct vmw_fpriv {
  */
 struct vmw_buffer_object {
 	struct ttm_buffer_object base;
-	struct list_head res_list;
+	struct rb_root res_tree;
 	s32 pin_count;
 	atomic_t cpu_writers;
 	/* Not ref-counted.  Protected by binding_mutex */
@@ -160,8 +160,8 @@ struct vmw_res_func;
  * pin-count greater than zero. It is not on the resource LRU lists and its
  * backup buffer is pinned. Hence it can't be evicted.
  * @func: Method vtable for this resource. Immutable.
+ * @mob_node; Node for the MOB backup rbtree. Protected by @backup reserved.
  * @lru_head: List head for the LRU list. Protected by @dev_priv::resource_lock.
- * @mob_head: List head for the MOB backup list. Protected by @backup reserved.
  * @binding_head: List head for the context binding list. Protected by
  * the @dev_priv::binding_mutex
  * @res_free: The resource destructor.
@@ -182,8 +182,8 @@ struct vmw_resource {
 	unsigned long backup_offset;
 	unsigned long pin_count;
 	const struct vmw_res_func *func;
+	struct rb_node mob_node;
 	struct list_head lru_head;
-	struct list_head mob_head;
 	struct list_head binding_head;
 	struct vmw_resource_dirty *dirty;
 	void (*res_free) (struct vmw_resource *res);
@@ -737,7 +737,7 @@ void vmw_resource_dirty_update(struct vmw_resource *res, pgoff_t start,
  */
 static inline bool vmw_resource_mob_attached(const struct vmw_resource *res)
 {
-	return !list_empty(&res->mob_head);
+	return !RB_EMPTY_NODE(&res->mob_node);
 }
 
 /**

drivers/gpu/drm/vmwgfx/vmwgfx_resource.c

@@ -40,11 +40,24 @@
 void vmw_resource_mob_attach(struct vmw_resource *res)
 {
 	struct vmw_buffer_object *backup = res->backup;
+	struct rb_node **new = &backup->res_tree.rb_node, *parent = NULL;
 
 	dma_resv_assert_held(res->backup->base.base.resv);
 	res->used_prio = (res->res_dirty) ? res->func->dirty_prio :
 		res->func->prio;
-	list_add_tail(&res->mob_head, &backup->res_list);
+
+	while (*new) {
+		struct vmw_resource *this =
+			container_of(*new, struct vmw_resource, mob_node);
+
+		parent = *new;
+		new = (res->backup_offset < this->backup_offset) ?
+			&((*new)->rb_left) : &((*new)->rb_right);
+	}
+
+	rb_link_node(&res->mob_node, parent, new);
+	rb_insert_color(&res->mob_node, &backup->res_tree);
+
 	vmw_bo_prio_add(backup, res->used_prio);
 }
 
@@ -58,7 +71,8 @@ void vmw_resource_mob_detach(struct vmw_resource *res)
 
 	dma_resv_assert_held(backup->base.base.resv);
 	if (vmw_resource_mob_attached(res)) {
-		list_del_init(&res->mob_head);
+		rb_erase(&res->mob_node, &backup->res_tree);
+		RB_CLEAR_NODE(&res->mob_node);
 		vmw_bo_prio_del(backup, res->used_prio);
 	}
 }
@@ -204,8 +218,8 @@ int vmw_resource_init(struct vmw_private *dev_priv, struct vmw_resource *res,
 	res->res_free = res_free;
 	res->dev_priv = dev_priv;
 	res->func = func;
+	RB_CLEAR_NODE(&res->mob_node);
 	INIT_LIST_HEAD(&res->lru_head);
-	INIT_LIST_HEAD(&res->mob_head);
 	INIT_LIST_HEAD(&res->binding_head);
 	res->id = -1;
 	res->backup = NULL;
@@ -753,19 +767,20 @@ int vmw_resource_validate(struct vmw_resource *res, bool intr)
  */
 void vmw_resource_unbind_list(struct vmw_buffer_object *vbo)
 {
-
-	struct vmw_resource *res, *next;
 	struct ttm_validate_buffer val_buf = {
 		.bo = &vbo->base,
 		.num_shared = 0
 	};
 
 	dma_resv_assert_held(vbo->base.base.resv);
-	list_for_each_entry_safe(res, next, &vbo->res_list, mob_head) {
-		if (!res->func->unbind)
-			continue;
+	while (!RB_EMPTY_ROOT(&vbo->res_tree)) {
+		struct rb_node *node = vbo->res_tree.rb_node;
+		struct vmw_resource *res =
+			container_of(node, struct vmw_resource, mob_node);
+
+		if (!WARN_ON_ONCE(!res->func->unbind))
+			(void) res->func->unbind(res, res->res_dirty, &val_buf);
 
-		(void) res->func->unbind(res, res->res_dirty, &val_buf);
 		res->backup_dirty = true;
 		res->res_dirty = false;
 		vmw_resource_mob_detach(res);