Re: [PATCH] drm: cma: fix refcounting on the dmabuf import error path

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Joonyoung,

Thank you for the patch.

On Friday 05 July 2013 15:32:35 Joonyoung Shim wrote:
> From drm gem CMA helper, it wasn't fixed dma_buf refcount problem fixed
> by commit 011c228. This patch solves it.

Please add a "Cc:stable@vger.kernel.org" here.

> Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/gpu/drm/drm_gem_cma_helper.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
> b/drivers/gpu/drm/drm_gem_cma_helper.c index ce06397..3f3a12b 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -554,7 +554,6 @@ struct drm_gem_object *drm_gem_cma_dmabuf_import(struct
> drm_device *drm, * refcount on gem itself instead of f_count of dmabuf.
>  			 */
>  			drm_gem_object_reference(obj);
> -			dma_buf_put(dma_buf);
>  			return obj;
>  		}
>  	}
> @@ -573,6 +572,8 @@ struct drm_gem_object *drm_gem_cma_dmabuf_import(struct
> drm_device *drm, goto error_gem_free;
>  	}
> 
> +	get_dma_buf(dma_buf);
> +

As a side note, you have probably placed the get_dma_buf() call here to mimic 
the drm_prime.c code, but would there be anything wrong by placing it right 
before returning the GEM object ? The dma_buf_put() call could then be removed 
from the error path.

>  	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>  	if (IS_ERR_OR_NULL(sgt)) {
>  		ret = sgt ? PTR_ERR(sgt) : -ENOMEM;
> @@ -597,6 +598,7 @@ error_buf_unmap:
>  	dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
>  error_buf_detach:
>  	dma_buf_detach(dma_buf, attach);
> +	dma_buf_put(dma_buf);
>  error_gem_free:
>  	drm_gem_cma_free_object(&cma_obj->base);
>  	return ERR_PTR(ret);
-- 
Regards,

Laurent Pinchart