Re: [RFC 3/5] dma-buf/fence: add .get_fences() ops

[Chris Wilson]

On Thu, Jun 23, 2016 at 12:29:48PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> 
> get_fences() should return a copy of all fences in the fence as some
> fence subclass (such as fence_array) can store more than one fence at
> time.
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> ---
>  drivers/dma-buf/fence.c | 14 ++++++++++++++
>  include/linux/fence.h   |  3 +++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/dma-buf/fence.c b/drivers/dma-buf/fence.c
> index 4e61afb..f4094fd 100644
> --- a/drivers/dma-buf/fence.c
> +++ b/drivers/dma-buf/fence.c
> @@ -185,6 +185,20 @@ void fence_release(struct kref *kref)
>  }
>  EXPORT_SYMBOL(fence_release);
>  
> +struct fence **fence_get_fences(struct fence *fence)

Returning an array, but not telling the caller how many elements in the
array?

> +{
> +	if (fence->ops->get_fences) {
> +		return fence->ops->get_fences(fence);
> +	} else {
> +		struct fence **fences = kmalloc(sizeof(**fences), GFP_KERNEL);

One too many * (=> sizeof(struct fence), not sizeof(struct fence *))

return kmemdup(&fence, sizeof(fence), GFP_KERNEL);

The documentation should emphasize that the fences in the
returned array have a "borrowed" reference (i.e. it does not return a
new reference to each fence).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre