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

From: Joonyoung Shim <jy0922.shim@samsung.com>
To: Inki Dae <inki.dae@samsung.com>, dri-devel@lists.freedesktop.org
Cc: sw0312.kim@samsung.com
Subject: Re: [PATCH 09/14] drm/exynos: remove call to drm_gem_free_mmap_offset()
Date: Mon, 17 Aug 2015 14:29:52 +0900	[thread overview]
Message-ID: <55D17150.4020109@samsung.com> (raw)
In-Reply-To: <55D01AA6.9080507@samsung.com>

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@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.
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