linux-kernel - Re: [PATCH] drm/v3d: Use kvcalloc

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Date:   Tue, 29 Mar 2022 17:31:47 +0530
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     Melissa Wen <mwen@...lia.com>
Cc:     Emma Anholt <emma@...olt.net>, David Airlie <airlied@...ux.ie>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        dan.carpenter@...cle.com, Melissa Wen <mwen@...lia.com>
Subject: Re: [PATCH] drm/v3d: Use kvcalloc

On 28/03/22 5:55 pm, Melissa Wen wrote:
> On 03/12, Harshit Mogalapalli wrote:
>> kvcalloc is same as kvmalloc_array + __GFP_ZERO.
>>
>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
>> ---
>>   drivers/gpu/drm/v3d/v3d_gem.c | 5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
>> index c7ed2e1cbab6..f7d37228461e 100644
>> --- a/drivers/gpu/drm/v3d/v3d_gem.c
>> +++ b/drivers/gpu/drm/v3d/v3d_gem.c
>> @@ -308,9 +308,8 @@ v3d_lookup_bos(struct drm_device *dev,
>>   		return -EINVAL;
>>   	}
>>   
>> -	job->bo = kvmalloc_array(job->bo_count,
>> -				 sizeof(struct drm_gem_cma_object *),
>> -				 GFP_KERNEL | __GFP_ZERO);
>> +	job->bo = kvcalloc(job->bo_count, sizeof(struct drm_gem_cma_object *),
>> +			   GFP_KERNEL);
> 
> Hi Harshit,
> Hi Melissa,

> This change seems valid to me, but I believe, in this point, v3d should
> move to use the DRM function `drm_gem_objects_lookup()`, and then your
> change goes there, since drm_get_objects_lookup() has the same issue
> you're pointing. What do you think?
> 
Thanks for looking at the patch.

Yes, you are right, the issue is same there as well.

Few other similar instances in drm/ subsystem.

drivers/gpu/drm/drm_gem.c:700 drm_gem_objects_lookup() warn: Please 
consider using kvcalloc instead
drivers/gpu/drm/ttm/ttm_tt.c:99 ttm_tt_alloc_page_directory() warn: 
Please consider using kvcalloc instead
drivers/gpu/drm/ttm/ttm_tt.c:108 ttm_dma_tt_alloc_page_directory() warn: 
Please consider using kvcalloc instead
drivers/gpu/drm/ttm/ttm_tt.c:121 ttm_sg_tt_alloc_page_directory() warn: 
Please consider using kvcalloc instead
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c:541 amdgpu_cs_parser_bos() warn: 
Please consider using kvcalloc instead
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_svm.c:152 
svm_range_dma_map_dev() warn: Please consider using kvcalloc instead
drivers/gpu/drm/v3d/v3d_gem.c:311 v3d_lookup_bos() warn: Please consider 
using kvcalloc instead
drivers/gpu/drm/vc4/vc4_gem.c:746 vc4_cl_lookup_bos() warn: Please 
consider using kvcalloc instead
drivers/gpu/drm/lima/lima_gem.c:42 lima_heap_alloc() warn: Please 
consider using kvcalloc instead
drivers/gpu/drm/panfrost/panfrost_drv.c:147 panfrost_lookup_bos() warn: 
Please consider using kvcalloc instead
drivers/gpu/drm/panfrost/panfrost_mmu.c:452 
panfrost_mmu_map_fault_addr() warn: Please consider using kvcalloc instead
drivers/gpu/drm/panfrost/panfrost_mmu.c:460 
panfrost_mmu_map_fault_addr() warn: Please consider using kvcalloc instead

Tool Used: Smatch.

> I already sent a patchset to replace steps in v3d_lookup_bos() by
> drm_gem_objects_lookup(), as I mentioned. The patchset is here:
> https://patchwork.freedesktop.org/series/101610/
> Willing to review it? ^
> 

Sorry Melissa, I am still a beginner, Can't review it.

Regards,
Harshit

> Thanks,
> 
> Melissa
> 
>>   	if (!job->bo) {
>>   		DRM_DEBUG("Failed to allocate validated BO pointers\n");
>>   		return -ENOMEM;
>> -- 
>> 2.31.1
>>