[PATCH v3 -next 4/9] DMA, CMA: support arbitrary bitmap granularity

Andrew Morton
2014-06-18T20:48:15Z

On Mon, 16 Jun 2014 14:40:46 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:

> PPC KVM's CMA area management requires arbitrary bitmap granularity,
> since they want to reserve very large memory and manage this region
> with bitmap that one bit for several pages to reduce management overheads.
> So support arbitrary bitmap granularity for following generalization.
>
> ...
>
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -38,6 +38,7 @@ struct cma {
> unsigned long base_pfn;
> unsigned long count;
> unsigned long *bitmap;
> + unsigned int order_per_bit; /* Order of pages represented by one bit */
> struct mutex lock;
> };
>
> @@ -157,9 +158,37 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>
> static DEFINE_MUTEX(cma_mutex);
>
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> + return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}

Might want a "1UL << ..." here.

> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> + return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> + unsigned long pages)
> +{
> + return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}

Ditto. I'm not really sure what the compiler will do in these cases,
but would prefer not to rely on it anyway!

--- a/drivers/base/dma-contiguous.c~dma-cma-support-arbitrary-bitmap-granularity-fix
+++ a/drivers/base/dma-contiguous.c
@@ -160,7 +160,7 @@ static DEFINE_MUTEX(cma_mutex);

static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
{
- return (1 << (align_order >> cma->order_per_bit)) - 1;
+ return (1UL << (align_order >> cma->order_per_bit)) - 1;
}

static unsigned long cma_bitmap_maxno(struct cma *cma)
@@ -171,7 +171,7 @@ static unsigned long cma_bitmap_maxno(st
static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
unsigned long pages)
{
- return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
+ return ALIGN(pages, 1UL << cma->order_per_bit) >> cma->order_per_bit;
}

static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, int count)
_