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

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Date:	Mon, 30 Jan 2012 08:43:55 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	'Ohad Ben-Cohen' <ohad@...ery.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

Hello,

On Saturday, January 28, 2012 7:57 PM Ohad Ben-Cohen wrote:

> 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!

Did you managed to fix this issue?

> 
> 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.

Right, thanks for spotting it, I will squash it to the next release.

> 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);
> 

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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