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

[Inki Dae]

On 2015년 09월 24일 10:01, Joonyoung Shim wrote:
> 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?

Oops, sorry. Merged.

Thanks,
Inki Dae

> 
> Thanks.
>