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

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 26.06.20 um 19:39 schrieb Ruhl, Michael J:
>> -----Original Message-----
>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>> Christian König
>> Sent: Wednesday, June 24, 2020 9:36 AM
>> To: dri-devel@lists.freedesktop.org
>> 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@amd.com>
>> ---
>> 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?

Yes, everything else would be a bug.

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

The caller should not touch the member when an error occurred since it 
is certainly not initialized.

But it might be a good idea to zero initialize the structure by the 
caller just to be sure.

Thanks for the comment,
Christian.

>
> 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
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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