Re: [RFC][PATCH] staging: ion: Fix ion_cma_heap allocations

[Laura Abbott <labbott@redhat.com>]

On 12/07/2017 03:42 PM, John Stultz wrote:
> In trying to add support for drm_hwcomposer to HiKey,
> I've needed to utilize the ION CMA heap, and I've noticed
> problems with allocations on newer kernels failing.
> 
> It seems back with 204f672255c22 ("ion: Use CMA APIs directly"),
> the ion_cma_heap code was modified to use the CMA API, but
> kept the arguments as buffer lengths rather then number of pages.
> 
> This results in errors as we don't have enough pages in CMA to
> satisfy the exaggerated requests.
> 
> This patch converts the ion_cma_heap CMA API usage to properly
> request pages.
> 
> It also fixes a minor issue in the allocation where in the error
> path, the cma_release is called with the buffer->size value which
> hasn't yet been set.
> 
> I'm no memory expert so close review would be appreciated!
> 

Yup.

Acked-by: Laura Abbott <labbott@redhat.com>

> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Dmitry Shmidt <dimitrysh@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Amit Pundir <amit.pundir@linaro.org>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>   drivers/staging/android/ion/ion_cma_heap.c | 15 +++++++++++----
>   1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index dd5545d..b0fb895 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -39,9 +39,15 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>   	struct ion_cma_heap *cma_heap = to_cma_heap(heap);
>   	struct sg_table *table;
>   	struct page *pages;
> +	unsigned long size = PAGE_ALIGN(len);
> +	unsigned long nr_pages = size >> PAGE_SHIFT;
> +	unsigned long align = get_order(size);
>   	int ret;
>   
> -	pages = cma_alloc(cma_heap->cma, len, 0, GFP_KERNEL);
> +	if (align > CONFIG_CMA_ALIGNMENT)
> +                align = CONFIG_CMA_ALIGNMENT;
> +
> +	pages = cma_alloc(cma_heap->cma, nr_pages, align, GFP_KERNEL);
>   	if (!pages)
>   		return -ENOMEM;
>   
> @@ -53,7 +59,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>   	if (ret)
>   		goto free_mem;
>   
> -	sg_set_page(table->sgl, pages, len, 0);
> +	sg_set_page(table->sgl, pages, size, 0);
>   
>   	buffer->priv_virt = pages;
>   	buffer->sg_table = table;
> @@ -62,7 +68,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>   free_mem:
>   	kfree(table);
>   err:
> -	cma_release(cma_heap->cma, pages, buffer->size);
> +	cma_release(cma_heap->cma, pages, nr_pages);
>   	return -ENOMEM;
>   }
>   
> @@ -70,9 +76,10 @@ static void ion_cma_free(struct ion_buffer *buffer)
>   {
>   	struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);
>   	struct page *pages = buffer->priv_virt;
> +	unsigned long nr_pages = PAGE_ALIGN(buffer->size) >> PAGE_SHIFT;
>   
>   	/* release memory */
> -	cma_release(cma_heap->cma, pages, buffer->size);
> +	cma_release(cma_heap->cma, pages, nr_pages);
>   	/* release sg table */
>   	sg_free_table(buffer->sg_table);
>   	kfree(buffer->sg_table);
>