On Wed, Nov 05 2014, Gregory Fong wrote:
> The alignment in cma_alloc() was done w.r.t. the bitmap. This is a
> problem when, for example:
>
> - a device requires 16M (order 12) alignment
> - the CMA region is not 16 M aligned
>
> In such a case, can result with the CMA region starting at, say,
> 0x2f800000 but any allocation you make from there will be aligned from
> there. Requesting an allocation of 32 M with 16 M alignment will
> result in an allocation from 0x2f800000 to 0x31800000, which doesn't
> work very well if your strange device requires 16M alignment.
>
> Change to use bitmap_find_next_zero_area_off() to account for the
> difference in alignment at reserve-time and alloc-time.
>
> Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Signed-off-by: Gregory Fong <gregory.0xf0@xxxxxxxxx>
> ---
> mm/cma.c | 19 ++++++++++++++++---
> 1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index fde706e..0813599 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -63,6 +63,17 @@ static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> return (1UL << (align_order - cma->order_per_bit)) - 1;
> }
>
> +static unsigned long cma_bitmap_aligned_offset(struct cma *cma, int align_order)
> +{
> + unsigned int alignment;
> +
> + if (align_order <= cma->order_per_bit)
> + return 0;
> + alignment = 1UL << (align_order - cma->order_per_bit);
> + return ALIGN(cma->base_pfn, alignment) -
> + (cma->base_pfn >> cma->order_per_bit);
> +}
> +
> static unsigned long cma_bitmap_maxno(struct cma *cma)
> {
> return cma->count >> cma->order_per_bit;
> @@ -328,7 +339,7 @@ err:
> */
> struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> {
> - unsigned long mask, pfn, start = 0;
> + unsigned long mask, offset, pfn, start = 0;
> unsigned long bitmap_maxno, bitmap_no, bitmap_count;
> struct page *page = NULL;
> int ret;
> @@ -343,13 +354,15 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
> return NULL;
>
> mask = cma_bitmap_aligned_mask(cma, align);
> + offset = cma_bitmap_aligned_offset(cma, align);
> bitmap_maxno = cma_bitmap_maxno(cma);
> bitmap_count = cma_bitmap_pages_to_bits(cma, count);
>
> for (;;) {
> mutex_lock(&cma->lock);
> - bitmap_no = bitmap_find_next_zero_area(cma->bitmap,
> - bitmap_maxno, start, bitmap_count, mask);
> + bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap,
> + bitmap_maxno, start, bitmap_count, mask,
> + offset);
> if (bitmap_no >= bitmap_maxno) {
> mutex_unlock(&cma->lock);
> break;
> --
> 1.9.1
>
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +--<mpn@xxxxxxxxxx>--<xmpp:mina86@xxxxxxxxxx>--ooO--(_)--Ooo--
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href