drm/ttm: add ttm_bo_move_to_lru_tail function v2

BugLink: http://bugs.launchpad.net/bugs/1546572

This allows the drivers to move a BO to the end of the LRU
without removing and adding it again.

v2: Make it more robust, handle pinned and swapable BOs as well.
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ab749618)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -228,6 +228,27 @@ void ttm_bo_del_sub_from_lru(struct ttm_buffer_object *bo)
 }
 EXPORT_SYMBOL(ttm_bo_del_sub_from_lru);
 
+void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo)
+{
+	struct ttm_bo_device *bdev = bo->bdev;
+	struct ttm_mem_type_manager *man;
+
+	lockdep_assert_held(&bo->resv->lock.base);
+
+	if (bo->mem.placement & TTM_PL_FLAG_NO_EVICT) {
+		list_del_init(&bo->swap);
+		list_del_init(&bo->lru);
+
+	} else {
+		if (bo->ttm && !(bo->ttm->page_flags & TTM_PAGE_FLAG_SG))
+			list_move_tail(&bo->swap, &bo->glob->swap_lru);
+
+		man = &bdev->man[bo->mem.mem_type];
+		list_move_tail(&bo->lru, &man->lru);
+	}
+}
+EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
+
 /*
  * Call bo->mutex locked.
  */

include/drm/ttm/ttm_bo_api.h

@@ -383,6 +383,16 @@ extern void ttm_bo_add_to_lru(struct ttm_buffer_object *bo);
  */
 extern int ttm_bo_del_from_lru(struct ttm_buffer_object *bo);
 
+/**
+ * ttm_bo_move_to_lru_tail
+ *
+ * @bo: The buffer object.
+ *
+ * Move this BO to the tail of all lru lists used to lookup and reserve an
+ * object. This function must be called with struct ttm_bo_global::lru_lock
+ * held, and is used to make a BO less likely to be considered for eviction.
+ */
+extern void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo);
 
 /**
  * ttm_bo_lock_delayed_workqueue