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

Ohad Ben-Cohen
2012-01-28T18:57:34Z

Hi Marek,

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!

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.

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);

Thanks,
Ohad.