[PATCH v3] drm: modify drm_global_item_ref to avoid two times of writing ref->object

[Christian König]

Am 08.09.2016 um 04:07 schrieb Huang Rui:
> In previous drm_global_item_ref, there are two times of writing
> ref->object if item->refcount is 0. So this patch does a minor update
> to put alloc and init ref firstly, and then to modify the item of glob
> array. Use "else" to avoid two times of writing ref->object. It can
> make the code logic more clearly.
>
> Signed-off-by: Huang Rui <ray.huang at amd.com>

Reviewed-by: Christian König <christian.koenig at amd.com>.

> ---
>
> Changes from V2 -> V3:
> - Use duplicate mutex release to avoid "goto" in non-error patch.
> - Rename error label
>
> ---
>   drivers/gpu/drm/drm_global.c | 24 ++++++++++++++----------
>   1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c
> index 3d2e91c..b404287 100644
> --- a/drivers/gpu/drm/drm_global.c
> +++ b/drivers/gpu/drm/drm_global.c
> @@ -65,30 +65,34 @@ void drm_global_release(void)
>   
>   int drm_global_item_ref(struct drm_global_reference *ref)
>   {
> -	int ret;
> +	int ret = 0;
>   	struct drm_global_item *item = &glob[ref->global_type];
>   
>   	mutex_lock(&item->mutex);
>   	if (item->refcount == 0) {
> -		item->object = kzalloc(ref->size, GFP_KERNEL);
> -		if (unlikely(item->object == NULL)) {
> +		ref->object = kzalloc(ref->size, GFP_KERNEL);
> +		if (unlikely(ref->object == NULL)) {
>   			ret = -ENOMEM;
> -			goto out_err;
> +			goto error_unlock;
>   		}
> -
> -		ref->object = item->object;
>   		ret = ref->init(ref);
>   		if (unlikely(ret != 0))
> -			goto out_err;
> +			goto error_free;
>   
> +		item->object = ref->object;
> +	} else {
> +		ref->object = item->object;
>   	}
> +
>   	++item->refcount;
> -	ref->object = item->object;
>   	mutex_unlock(&item->mutex);
>   	return 0;
> -out_err:
> +
> +error_free:
> +	kfree(ref->object);
> +	ref->object = NULL;
> +error_unlock:
>   	mutex_unlock(&item->mutex);
> -	item->object = NULL;
>   	return ret;
>   }
>   EXPORT_SYMBOL(drm_global_item_ref);