drm/ttm: cleanup ttm_mem_type_manager_func.get_node interface v3

Instead of signaling failure by setting the node pointer to
NULL do so by returning -ENOSPC.

v2: add memset() to make sure that mem is always initialized.
v3: drop memset() only set mm_node = NULL, move mm_node init in amdgpu

Signed-off-by: Christian König <[e-mail]>
Reviewed-by: Michael J. Ruhl <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/373181/

drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c

···
 	if ((&tbo->mem == mem || tbo->mem.mem_type != TTM_PL_TT) &&
 	    atomic64_read(&mgr->available) < mem->num_pages) {
 		spin_unlock(&mgr->lock);
-		return 0;
+		return -ENOSPC;
 	}
 	atomic64_sub(mem->num_pages, &mgr->available);
 	spin_unlock(&mgr->lock);
···
 		if (unlikely(r)) {
 			kfree(node);
 			mem->mm_node = NULL;
-			r = 0;
 			goto err_out;
 		}
 	} else {

drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

···
 	mem_bytes = (u64)mem->num_pages << PAGE_SHIFT;
 	if (atomic64_add_return(mem_bytes, &mgr->usage) > max_bytes) {
 		atomic64_sub(mem_bytes, &mgr->usage);
-		mem->mm_node = NULL;
-		return 0;
+		return -ENOSPC;
 	}
 
 	if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
···
 	atomic64_sub(mem->num_pages << PAGE_SHIFT, &mgr->usage);
 
 	kvfree(nodes);
-	return r == -ENOSPC ? 0 : r;
+	return r;
 }
 
 /**

drivers/gpu/drm/nouveau/nouveau_ttm.c

···
 	ret = nouveau_mem_vram(reg, nvbo->contig, nvbo->page);
 	if (ret) {
 		nouveau_mem_del(reg);
-		if (ret == -ENOSPC) {
-			reg->mm_node = NULL;
-			return 0;
-		}
 		return ret;
 	}
 
···
 			   reg->num_pages << PAGE_SHIFT, &mem->vma[0]);
 	if (ret) {
 		nouveau_mem_del(reg);
-		if (ret == -ENOSPC) {
-			reg->mm_node = NULL;
-			return 0;
-		}
 		return ret;
 	}
 

drivers/gpu/drm/ttm/ttm_bo.c

···
 	ticket = dma_resv_locking_ctx(bo->base.resv);
 	do {
 		ret = (*man->func->get_node)(man, bo, place, mem);
-		if (unlikely(ret != 0))
-			return ret;
-		if (mem->mm_node)
+		if (likely(!ret))
 			break;
+		if (unlikely(ret != -ENOSPC))
+			return ret;
 		ret = ttm_mem_evict_first(bdev, mem->mem_type, place, ctx,
 					  ticket);
 		if (unlikely(ret != 0))
···
 
 		man = &bdev->man[mem->mem_type];
 		ret = (*man->func->get_node)(man, bo, place, mem);
+		if (ret == -ENOSPC)
+			continue;
 		if (unlikely(ret))
 			goto error;
-
-		if (!mem->mm_node)
-			continue;
 
 		ret = ttm_bo_add_move_fence(bo, man, mem, ctx->no_wait_gpu);
 		if (unlikely(ret)) {
···
 	mem.page_alignment = bo->mem.page_alignment;
 	mem.bus.io_reserved_vm = false;
 	mem.bus.io_reserved_count = 0;
+	mem.mm_node = NULL;
+
 	/*
 	 * Determine where to move the buffer.
 	 */

drivers/gpu/drm/ttm/ttm_bo_manager.c

···
 		mem->start = node->start;
 	}
 
-	return 0;
+	return ret;
 }
 
 static void ttm_bo_man_put_node(struct ttm_mem_type_manager *man,

drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c

···
 		(struct vmwgfx_gmrid_man *)man->priv;
 	int id;
 
-	mem->mm_node = NULL;
-
 	id = ida_alloc_max(&gman->gmr_ida, gman->max_gmr_ids - 1, GFP_KERNEL);
 	if (id < 0)
 		return (id != -ENOMEM ? 0 : id);
···
 	gman->used_gmr_pages -= bo->num_pages;
 	spin_unlock(&gman->lock);
 	ida_free(&gman->gmr_ida, id);
-	return 0;
+	return -ENOSPC;
 }
 
 static void vmw_gmrid_man_put_node(struct ttm_mem_type_manager *man,