RE: [Linaro-mm-sig] [PATCH 12/15] drivers: add Contiguous Memory Allocator

Marek Szyprowski
2012-01-30T07:44:02Z

Hello,

On Saturday, January 28, 2012 7:57 PM Ohad Ben-Cohen wrote:

> On Fri, Jan 27, 2012 at 5:17 PM, Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
> > There have been some vmalloc layout changes merged to v3.3-rc1.
>
> That was dead-on, thanks a lot!

Did you managed to fix this issue?

>
> I did then bump into a different allocation failure which happened
> because dma_alloc_from_contiguous() computes 'mask' before capping the
> 'align' argument.
>
> The early 'mask' computation was added in v18 (and therefore exists in
> v19 too) and I was actually testing v17 previously, so I didn't notice
> it before.

Right, thanks for spotting it, I will squash it to the next release.

> You may want to squash something like this:
>
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index f41e699..8455cb7 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -319,8 +319,7 @@ struct page *dma_alloc_from_contiguous(struct device *dev, i
> unsigned int align)
> {
> struct cma *cma = dev_get_cma_area(dev);
> - unsigned long pfn, pageno, start = 0;
> - unsigned long mask = (1 << align) - 1;
> + unsigned long mask, pfn, pageno, start = 0;
> int ret;
>
> if (!cma || !cma->count)
> @@ -329,6 +328,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, i
> if (align > CONFIG_CMA_ALIGNMENT)
> align = CONFIG_CMA_ALIGNMENT;
>
> + mask = (1 << align) - 1;
> +
> pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
> count, align);
>

Best regards
--
Marek Szyprowski
Samsung Poland R&D Center