2012-08-24 07:20:41

by Marek Szyprowski

[permalink] [raw]
Subject: [PATCH] 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 <[email protected]>
CC: Michal Nazarewicz <[email protected]>
---
drivers/base/dma-contiguous.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 78efb03..34d94c7 100644
--- 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);
--
1.7.1.569.g6f426