[PATCH 09/14] drm/exynos: remove call to drm_gem_free_mmap_offset()

[Joonyoung Shim]

Hi Inki,

On 08/17/2015 06:03 PM, Inki Dae wrote:
> On 2015년 08월 17일 17:17, Joonyoung Shim wrote:
>> On 08/17/2015 04:52 PM, Inki Dae wrote:
>>> On 2015년 08월 17일 14:29, Joonyoung Shim wrote:
>>>> On 08/16/2015 02:07 PM, Inki Dae wrote:
>>>>> On 2015년 07월 28일 17:53, Joonyoung Shim wrote:
>>>>>> The drm_gem_object_release() function already performs this cleanup,
>>>>>> so there is no reason to do it explicitly.
>>>>>>
>>>>>> Signed-off-by: Joonyoung Shim <jy0922.shim at samsung.com>
>>>>>> ---
>>>>>>  drivers/gpu/drm/exynos/exynos_drm_gem.c | 3 ---
>>>>>>  1 file changed, 3 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
>>>>>> index c76aa8a..ab7d029 100644
>>>>>> --- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
>>>>>> +++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
>>>>>> @@ -100,8 +100,6 @@ out:
>>>>>>  	exynos_drm_fini_buf(obj->dev, buf);
>>>>>>  	exynos_gem_obj->buffer = NULL;
>>>>>>  
>>>>>> -	drm_gem_free_mmap_offset(obj);
>>>>>> -
>>>>>>  	/* release file pointer to gem object. */
>>>>>>  	drm_gem_object_release(obj);
>>>>>>  
>>>>>> @@ -600,7 +598,6 @@ int exynos_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>>>>>>  
>>>>>>  err_close_vm:
>>>>>>  	drm_gem_vm_close(vma);
>>>>>> -	drm_gem_free_mmap_offset(obj);
>>>>>
>>>>> Without previous patch, drm_gem_free_mmap_offset is required. I guess
>>>>> the reason you removed above line is that you thought
>>>>> drm_gem_object_release function would be called by drm_gem_vm_close
>>>>> function which drops a reference of the gem object.
>>>>>
>>>>> However, drm_gem_vm_close should be a pair with drm_gem_vm_open
>>>>> function. These will be called whenever a process opens or closes the
>>>>> VMA. So the reference count of the gem object had already been taken by
>>>>> open operation when a new reference to the VMA had been created.
>>>>>
>>>>
>>>> This changes is not related with drm_gem_vm_close and prior patch. Why
>>>> should free mmap offset when mmap operation is failed? The mmap offset
>>>> can be used repeatedly.
>>>
>>> Isn't vm space of vm manager still used even if any user-space process
>>> doesn't use the region? And if mmap is failed, then the user-space
>>> process will be terminated. Do you think it can be re-tried? However,
>>> mmap system call never return -EAGAIN. Is it reasonable to you? I cannot
>>> understand how the mmap offset can be re-used. So can you show me some
>>> example?
>>>
>>
>> Currently, mmap offset of exynos-drm gem is made by                 
>> DRM_IOCTL_MODE_MAP_DUMB ioctl and mmap() ioctl just uses the mmap     
>> offset. User will use same mmap offset about same gem. It's why mmap
>> offset made by DRM_IOCTL_MODE_MAP_DUMB ioctl is unnecessary, it's just
>> enough to make mmap offset from when gem is create. You can get a
>> reference from drm_gem_cma_helper.c file.
> 
> Hmm... It's not that the mmap offset can be re-used or not. It's that
> the mmap offset should be released or not when mmap failed. As your
> original comment, the call of drm_gem_free_mmap_offset() is unnecessary
> if mmap offset is created when gem creation because the mmap offset is
> removed by drm_gem_object_release() when gem is destroyed - gem should
> also be released when mmap failed.
> 
> Ok, let's create mmap offset at gem creation and remove it gem
> releasing. Will merge these two patches.
> 

I can't find them from your git. Could you merge them?

Thanks.