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

Joonsoo Kim
2014-06-19T08:18:07Z

On Wed, Jun 18, 2014 at 01:48:15PM -0700, Andrew Morton wrote:
> 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.

Okay!

>
> > +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!

Okay!

Thanks for fix!