From: Marek Szyprowski <m.szyprowski@samsung.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linaro-mm-sig@lists.linaro.org
Cc: Michal Nazarewicz <mina86@mina86.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mel@csn.ul.ie>,
        Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH] mm: cma: fix alignment requirements for contiguous regions
Date: Fri, 24 Aug 2012 09:20:10 +0200
Message-id: <1345792810-5152-1-git-send-email-m.szyprowski@samsung.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1372
Lines: 34

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>
---
 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

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