mm: cma: fix alignment requirements for contiguous regions

Contiguous Memory Allocator requires each of its regions to be aligned
in such a way that it is possible to change migration type for all
pageblocks holding it and then isolate page of largest possible order from
the buddy allocator (which is MAX_ORDER-1). This patch relaxes alignment
requirements by one order, because MAX_ORDER alignment is not really
needed.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
CC: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>

diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 78efb03..34d94c7 100644 (file)
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c
@@ -250,7 +250,7 @@ int __init dma_declare_contiguous(struct device *dev, unsigned long size,
                return -EINVAL;
 
        /* Sanitise input arguments */
-       alignment = PAGE_SIZE << max(MAX_ORDER, pageblock_order);
+       alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
        base = ALIGN(base, alignment);
        size = ALIGN(size, alignment);
        limit &= ~(alignment - 1);