RE: [PATCH 1/2] drm/ttm: cleanup ttm_mem_type_manager_func.get_node interface

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>-----Original Message-----
>From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>Christian König
>Sent: Wednesday, June 24, 2020 9:36 AM
>To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
>Subject: [PATCH 1/2] drm/ttm: cleanup
>ttm_mem_type_manager_func.get_node interface
>
>Instead of signaling failure by setting the node pointer to
>NULL do so by returning -ENOSPC.
>
>Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>---
> drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c   |  4 +---
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c  |  5 ++---
> drivers/gpu/drm/nouveau/nouveau_ttm.c         |  8 --------
> drivers/gpu/drm/ttm/ttm_bo.c                  | 11 +++++------
> drivers/gpu/drm/ttm/ttm_bo_manager.c          |  2 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c |  4 +---
> 6 files changed, 10 insertions(+), 24 deletions(-)
>
>diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
>b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
>index 627104401e84..2baa80224fa4 100644
>--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
>+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
>@@ -229,7 +229,7 @@ static int amdgpu_gtt_mgr_new(struct
>ttm_mem_type_manager *man,
> 	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);
>@@ -249,8 +249,6 @@ static int amdgpu_gtt_mgr_new(struct
>ttm_mem_type_manager *man,
> 		r = amdgpu_gtt_mgr_alloc(man, tbo, place, mem);
> 		if (unlikely(r)) {
> 			kfree(node);
>-			mem->mm_node = NULL;

Hmm, amdgpu_gtt_mgr_del() grabs mem->mm_node and kfrees it.

If this value is not NUL, it looks like bad things could happen.

Will _mgr_del never get called in this case?

Using the return value seems pretty reasonable, leaving bad pointers
lying around makes me slightly nervous.

Mike

>-			r = 0;
> 			goto err_out;
> 		}
> 	} else {
>diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>index 128a667ed8fa..e8d1dd564006 100644
>--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>@@ -336,8 +336,7 @@ static int amdgpu_vram_mgr_new(struct
>ttm_mem_type_manager *man,
> 	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) {
>@@ -417,7 +416,7 @@ static int amdgpu_vram_mgr_new(struct
>ttm_mem_type_manager *man,
> 	atomic64_sub(mem->num_pages << PAGE_SHIFT, &mgr->usage);
>
> 	kvfree(nodes);
>-	return r == -ENOSPC ? 0 : r;
>+	return r;
> }
>
> /**
>diff --git a/drivers/gpu/drm/nouveau/nouveau_ttm.c
>b/drivers/gpu/drm/nouveau/nouveau_ttm.c
>index 7ca0a2498532..e89ea052cf71 100644
>--- a/drivers/gpu/drm/nouveau/nouveau_ttm.c
>+++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c
>@@ -75,10 +75,6 @@ nouveau_vram_manager_new(struct
>ttm_mem_type_manager *man,
> 	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;
> 	}
>
>@@ -139,10 +135,6 @@ nv04_gart_manager_new(struct
>ttm_mem_type_manager *man,
> 			   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;
> 	}
>
>diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>index f73b81c2576e..15f9b19fa00d 100644
>--- a/drivers/gpu/drm/ttm/ttm_bo.c
>+++ b/drivers/gpu/drm/ttm/ttm_bo.c
>@@ -916,10 +916,10 @@ static int ttm_bo_mem_force_space(struct
>ttm_buffer_object *bo,
> 	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))
>@@ -1063,12 +1063,11 @@ int ttm_bo_mem_space(struct ttm_buffer_object
>*bo,
>
> 		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)) {
> 			(*man->func->put_node)(man, mem);
>diff --git a/drivers/gpu/drm/ttm/ttm_bo_manager.c
>b/drivers/gpu/drm/ttm/ttm_bo_manager.c
>index 18d3debcc949..facd3049c3aa 100644
>--- a/drivers/gpu/drm/ttm/ttm_bo_manager.c
>+++ b/drivers/gpu/drm/ttm/ttm_bo_manager.c
>@@ -86,7 +86,7 @@ static int ttm_bo_man_get_node(struct
>ttm_mem_type_manager *man,
> 		mem->start = node->start;
> 	}
>
>-	return 0;
>+	return ret;
> }
>
> static void ttm_bo_man_put_node(struct ttm_mem_type_manager *man,
>diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
>b/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
>index 7da752ca1c34..4a76fc7114ad 100644
>--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
>+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gmrid_manager.c
>@@ -53,8 +53,6 @@ static int vmw_gmrid_man_get_node(struct
>ttm_mem_type_manager *man,
> 		(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);
>@@ -78,7 +76,7 @@ static int vmw_gmrid_man_get_node(struct
>ttm_mem_type_manager *man,
> 	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,
>--
>2.17.1
>
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