linux-kernel - Re: [RFC][PATCH] CMA: drivers/base/Kconfig: restrict CMA size to non-zero value

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Message-ID: <xa1td2f91qw5.fsf@mina86.com>
Date:	Mon, 19 May 2014 09:59:22 -1000
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>, Gioh Kim <gioh.kim@....com>
Cc:	Minchan Kim <minchan.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Laura Abbott <lauraa@...eaurora.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Heesub Shin <heesub.shin@...sung.com>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	이건호 <gunho.lee@....com>, gurugio@...il.com
Subject: Re: [RFC][PATCH] CMA: drivers/base/Kconfig: restrict CMA size to non-zero value

On Sun, May 18 2014, Joonsoo Kim wrote:
> I think that this problem is originated from atomic_pool_init().
> If configured coherent_pool size is larger than default cma size,
> it can be failed even if this patch is applied.
>
> How about below patch?
> It uses fallback allocation if CMA is failed.

Yes, I thought about it, but __dma_alloc uses similar code:

	else if (!IS_ENABLED(CONFIG_DMA_CMA))
		addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller);
	else
		addr = __alloc_from_contiguous(dev, size, prot, &page, caller);

so it probably needs to be changed as well.

> -----------------8<---------------------
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 6b00be1..2909ab9 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -379,7 +379,7 @@ static int __init atomic_pool_init(void)
>         unsigned long *bitmap;
>         struct page *page;
>         struct page **pages;
> -       void *ptr;
> +       void *ptr = NULL;
>         int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
>  
>         bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> @@ -393,7 +393,7 @@ static int __init atomic_pool_init(void)
>         if (IS_ENABLED(CONFIG_DMA_CMA))
>                 ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page,
>                                               atomic_pool_init);
> -       else
> +       if (!ptr)
>                 ptr = __alloc_remap_buffer(NULL, pool->size, gfp, prot, &page,
>                                            atomic_pool_init);
>         if (ptr) {
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--


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