[PATCH 3.18 09/24] mm: cma: align to physical address, not CMA region position

Greg Kroah-Hartman
2017-08-31T15:51:29Z

From: Gregory Fong <gregory.0xf0@gmail.com>

commit b5be83e308f70e16c63c4e520ea7bb03ef57c46f upstream.

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.

Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/cma.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

--- a/mm/cma.c
+++ b/mm/cma.c
@@ -63,6 +63,17 @@ static unsigned long cma_bitmap_aligned_
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;
@@ -341,7 +352,7 @@ 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;
@@ -356,13 +367,15 @@ struct page *cma_alloc(struct cma *cma,
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;