linux-kernel - Re: [Linaro-mm-sig] [PATCH 12/15] drivers: add Contiguous Memory Allocator

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Date:	Sat, 28 Jan 2012 20:57:14 +0200
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	"Clark, Rob" <rob@...com>, Daniel Walker <dwalker@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>, Mel Gorman <mel@....ul.ie>,
	Jesse Barker <jesse.barker@...aro.org>,
	linux-kernel@...r.kernel.org,
	Michal Nazarewicz <mina86@...a86.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [Linaro-mm-sig] [PATCH 12/15] drivers: add Contiguous Memory Allocator

Hi Marek,

On Fri, Jan 27, 2012 at 5:17 PM, Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
> There have been some vmalloc layout changes merged to v3.3-rc1.

That was dead-on, thanks a lot!

I did then bump into a different allocation failure which happened
because dma_alloc_from_contiguous() computes 'mask' before capping the
'align' argument.

The early 'mask' computation was added in v18 (and therefore exists in
v19 too) and I was actually testing v17 previously, so I didn't notice
it before.

You may want to squash something like this:

diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index f41e699..8455cb7 100644
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c
@@ -319,8 +319,7 @@ struct page *dma_alloc_from_contiguous(struct device *dev, i
                                       unsigned int align)
 {
        struct cma *cma = dev_get_cma_area(dev);
-       unsigned long pfn, pageno, start = 0;
-       unsigned long mask = (1 << align) - 1;
+       unsigned long mask, pfn, pageno, start = 0;
        int ret;

        if (!cma || !cma->count)
@@ -329,6 +328,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, i
        if (align > CONFIG_CMA_ALIGNMENT)
                align = CONFIG_CMA_ALIGNMENT;

+       mask = (1 << align) - 1;
+
        pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
                 count, align);

Thanks,
Ohad.
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