linux-kernel - Re: [RESEND PATCH v2 3/9] x86, dma: Support allocate memory from bottom upwards in dma_contiguous

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Date:	Thu, 12 Sep 2013 13:22:39 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	tj@...nel.org, rjw@...k.pl, lenb@...nel.org, tglx@...utronix.de,
	mingo@...e.hu, hpa@...or.com, akpm@...ux-foundation.org,
	trenn@...e.de, yinghai@...nel.org, jiang.liu@...wei.com,
	wency@...fujitsu.com, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	mgorman@...e.de, minchan@...nel.org, mina86@...a86.com,
	gong.chen@...ux.intel.com, vasilis.liaskovitis@...fitbricks.com,
	lwoodman@...hat.com, riel@...hat.com, jweiner@...hat.com,
	prarit@...hat.com, zhangyanfei@...fujitsu.com, x86@...nel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-acpi@...r.kernel.org
Subject: Re: [RESEND PATCH v2 3/9] x86, dma: Support allocate memory from
 bottom upwards in dma_contiguous_reserve().

On Thu, 2013-09-12 at 17:52 +0800, Tang Chen wrote:
> During early boot, if the bottom up mode is set, just
> try allocating bottom up from the end of kernel image,
> and if that fails, do normal top down allocation.
> 
> So in function dma_contiguous_reserve(), we add the
> above logic.
> 
> Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
> Reviewed-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
> ---
>  drivers/base/dma-contiguous.c |   17 ++++++++++++++---
>  1 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 99802d6..aada945 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -228,17 +228,28 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  			goto err;
>  		}
>  	} else {
> +		phys_addr_t addr;
> +
> +		if (memblock_direction_bottom_up()) {
> +			addr = memblock_alloc_bottom_up(
> +						MEMBLOCK_ALLOC_ACCESSIBLE,
> +						limit, size, alignment);
> +			if (addr)
> +				goto success;
> +		}

I am afraid that this version went to a wrong direction.  Allocating
from the bottom up needs to be an internal logic within the memblock
allocator.  It should not require the callers to be aware of the
direction and make a special request.

Thanks,
-Toshi


> +
>  		/*
>  		 * Use __memblock_alloc_base() since
>  		 * memblock_alloc_base() panic()s.
>  		 */
> -		phys_addr_t addr = __memblock_alloc_base(size, alignment, limit);
> +		addr = __memblock_alloc_base(size, alignment, limit);
>  		if (!addr) {
>  			ret = -ENOMEM;
>  			goto err;
> -		} else {
> -			base = addr;
>  		}
> +
> +success:
> +		base = addr;
>  	}
>  
>  	/*


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