drm/ttm: add resource iterator v4

Instead of duplicating that at different places add an iterator over all
the resources in a resource manager.

v2: add lockdep annotation and kerneldoc
v3: fix various bugs pointed out by Felix
v4: simplify the code a bit more
Signed-off-by: Christian König <christian.koenig@amd.com>
Tested-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v2)
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321132601.2161-2-christian.koenig@amd.com

drivers/gpu/drm/ttm/ttm_bo.c

@@ -579,38 +579,29 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
 			struct ww_acquire_ctx *ticket)
 {
 	struct ttm_buffer_object *bo = NULL, *busy_bo = NULL;
+	struct ttm_resource_cursor cursor;
 	struct ttm_resource *res;
 	bool locked = false;
-	unsigned i;
 	int ret;
 
 	spin_lock(&bdev->lru_lock);
-	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
-		list_for_each_entry(res, &man->lru[i], lru) {
-			bool busy;
+	ttm_resource_manager_for_each_res(man, &cursor, res) {
+		bool busy;
+
+		if (!ttm_bo_evict_swapout_allowable(res->bo, ctx, place,
+						    &locked, &busy)) {
+			if (busy && !busy_bo && ticket !=
+			    dma_resv_locking_ctx(res->bo->base.resv))
+				busy_bo = res->bo;
+			continue;
+		}
 
+		if (ttm_bo_get_unless_zero(res->bo)) {
 			bo = res->bo;
-			if (!ttm_bo_evict_swapout_allowable(bo, ctx, place,
-							    &locked, &busy)) {
-				if (busy && !busy_bo && ticket !=
-				    dma_resv_locking_ctx(bo->base.resv))
-					busy_bo = bo;
-				continue;
-			}
-
-			if (!ttm_bo_get_unless_zero(bo)) {
-				if (locked)
-					dma_resv_unlock(bo->base.resv);
-				continue;
-			}
 			break;
 		}
-
-		/* If the inner loop terminated early, we have our candidate */
-		if (&res->lru != &man->lru[i])
-			break;
-
-		bo = NULL;
+		if (locked)
+			dma_resv_unlock(res->bo->base.resv);
 	}
 
 	if (!bo) {

drivers/gpu/drm/ttm/ttm_device.c

@@ -142,10 +142,10 @@ EXPORT_SYMBOL(ttm_global_swapout);
 int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 		       gfp_t gfp_flags)
 {
+	struct ttm_resource_cursor cursor;
 	struct ttm_resource_manager *man;
-	struct ttm_buffer_object *bo;
 	struct ttm_resource *res;
-	unsigned i, j;
+	unsigned i;
 	int ret;
 
 	spin_lock(&bdev->lru_lock);
@@ -154,20 +154,16 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 		if (!man || !man->use_tt)
 			continue;
 
-		for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
-			list_for_each_entry(res, &man->lru[j], lru) {
-				uint32_t num_pages;
-
-				bo = res->bo;
-				num_pages = PFN_UP(bo->base.size);
+		ttm_resource_manager_for_each_res(man, &cursor, res) {
+			struct ttm_buffer_object *bo = res->bo;
+			uint32_t num_pages = PFN_UP(bo->base.size);
 
-				ret = ttm_bo_swapout(bo, ctx, gfp_flags);
-				/* ttm_bo_swapout has dropped the lru_lock */
-				if (!ret)
-					return num_pages;
-				if (ret != -EBUSY)
-					return ret;
-			}
+			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
+			/* ttm_bo_swapout has dropped the lru_lock */
+			if (!ret)
+				return num_pages;
+			if (ret != -EBUSY)
+				return ret;
 		}
 	}
 	spin_unlock(&bdev->lru_lock);

drivers/gpu/drm/ttm/ttm_resource.c

@@ -385,6 +385,57 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 }
 EXPORT_SYMBOL(ttm_resource_manager_debug);
 
+/**
+ * ttm_resource_manager_first
+ *
+ * @man: resource manager to iterate over
+ * @cursor: cursor to record the position
+ *
+ * Returns the first resource from the resource manager.
+ */
+struct ttm_resource *
+ttm_resource_manager_first(struct ttm_resource_manager *man,
+			   struct ttm_resource_cursor *cursor)
+{
+	struct ttm_resource *res;
+
+	lockdep_assert_held(&man->bdev->lru_lock);
+
+	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
+	     ++cursor->priority)
+		list_for_each_entry(res, &man->lru[cursor->priority], lru)
+			return res;
+
+	return NULL;
+}
+
+/**
+ * ttm_resource_manager_next
+ *
+ * @man: resource manager to iterate over
+ * @cursor: cursor to record the position
+ * @res: the current resource pointer
+ *
+ * Returns the next resource from the resource manager.
+ */
+struct ttm_resource *
+ttm_resource_manager_next(struct ttm_resource_manager *man,
+			  struct ttm_resource_cursor *cursor,
+			  struct ttm_resource *res)
+{
+	lockdep_assert_held(&man->bdev->lru_lock);
+
+	list_for_each_entry_continue(res, &man->lru[cursor->priority], lru)
+		return res;
+
+	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
+	     ++cursor->priority)
+		list_for_each_entry(res, &man->lru[cursor->priority], lru)
+			return res;
+
+	return NULL;
+}
+
 static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
 					  struct dma_buf_map *dmap,
 					  pgoff_t i)

include/drm/ttm/ttm_resource.h

@@ -188,6 +188,17 @@ struct ttm_resource {
 	struct list_head lru;
 };
 
+/**
+ * struct ttm_resource_cursor
+ *
+ * @priority: the current priority
+ *
+ * Cursor to iterate over the resources in a manager.
+ */
+struct ttm_resource_cursor {
+	unsigned int priority;
+};
+
 /**
  * struct ttm_lru_bulk_move_pos
  *
@@ -333,6 +344,18 @@ uint64_t ttm_resource_manager_usage(struct ttm_resource_manager *man);
 void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 				struct drm_printer *p);
 
+struct ttm_resource *
+ttm_resource_manager_first(struct ttm_resource_manager *man,
+			   struct ttm_resource_cursor *cursor);
+struct ttm_resource *
+ttm_resource_manager_next(struct ttm_resource_manager *man,
+			  struct ttm_resource_cursor *cursor,
+			  struct ttm_resource *res);
+
+#define ttm_resource_manager_for_each_res(man, cursor, res)		\
+	for (res = ttm_resource_manager_first(man, cursor); res;	\
+	     res = ttm_resource_manager_next(man, cursor, res))
+
 struct ttm_kmap_iter *
 ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
 			 struct io_mapping *iomap,