drm/ttm/nouveau: don't call tt destroy callback on alloc failure.

This is confusing, and from my reading of all the drivers only
nouveau got this right.

Just make the API act under driver control of it's own allocation
failing, and don't call destroy, if the page table fails to
create there is nothing to cleanup here.

(I'm willing to believe I've missed something here, so please
review deeply).

Reviewed-by: Christian K├Ânig <christian.koenig@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200728041736.20689-1-airlied@gmail.com
diff --git a/drivers/gpu/drm/nouveau/nouveau_sgdma.c b/drivers/gpu/drm/nouveau/nouveau_sgdma.c
index 20b6d0b..c3ccf66 100644
--- a/drivers/gpu/drm/nouveau/nouveau_sgdma.c
+++ b/drivers/gpu/drm/nouveau/nouveau_sgdma.c
@@ -95,12 +95,9 @@
 	else
 		nvbe->ttm.ttm.func = &nv50_sgdma_backend;
 
-	if (ttm_dma_tt_init(&nvbe->ttm, bo, page_flags))
-		/*
-		 * A failing ttm_dma_tt_init() will call ttm_tt_destroy()
-		 * and thus our nouveau_sgdma_destroy() hook, so we don't need
-		 * to free nvbe here.
-		 */
+	if (ttm_dma_tt_init(&nvbe->ttm, bo, page_flags)) {
+		kfree(nvbe);
 		return NULL;
+	}
 	return &nvbe->ttm.ttm;
 }
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index bab6787..9d1c7177 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -244,7 +244,6 @@
 	ttm_tt_init_fields(ttm, bo, page_flags);
 
 	if (ttm_tt_alloc_page_directory(ttm)) {
-		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
 	}
@@ -268,7 +267,6 @@
 
 	INIT_LIST_HEAD(&ttm_dma->pages_list);
 	if (ttm_dma_tt_alloc_page_directory(ttm_dma)) {
-		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
 	}
@@ -290,7 +288,6 @@
 	else
 		ret = ttm_dma_tt_alloc_page_directory(ttm_dma);
 	if (ret) {
-		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
 	}