linux-kernel - Re: [PATCH v3 2/5] memblock: Improve memblock to support allocation from lower address.

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Date:	Fri, 13 Sep 2013 15:53:28 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	rjw@...k.pl, lenb@...nel.org, tglx@...utronix.de, mingo@...e.hu,
	hpa@...or.com, akpm@...ux-foundation.org, tj@...nel.org,
	zhangyanfei@...fujitsu.com, liwanp@...ux.vnet.ibm.com,
	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, x86@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 2/5] memblock: Improve memblock to support allocation
 from lower address.

On Fri, 2013-09-13 at 17:30 +0800, Tang Chen wrote:
 :
> @@ -100,8 +180,7 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start,
>  					phys_addr_t end, phys_addr_t size,
>  					phys_addr_t align, int nid)
>  {
> -	phys_addr_t this_start, this_end, cand;
> -	u64 i;
> +	phys_addr_t ret;
>  
>  	/* pump up @end */
>  	if (end == MEMBLOCK_ALLOC_ACCESSIBLE)
> @@ -111,18 +190,22 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start,
>  	start = max_t(phys_addr_t, start, PAGE_SIZE);
>  	end = max(start, end);
>  
> -	for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) {
> -		this_start = clamp(this_start, start, end);
> -		this_end = clamp(this_end, start, end);
> +	if (memblock_direction_bottom_up()) {
> +		/*
> +		 * MEMBLOCK_ALLOC_ACCESSIBLE is 0, which is less than the end
> +		 * of kernel image. So callers specify MEMBLOCK_ALLOC_ACCESSIBLE
> +		 * as @start is OK.
> +		 */
> +		start =	max(start, __pa_symbol(_end)); /* End of kernel image. */
>  
> -		if (this_end < size)
> -			continue;
> +		ret = __memblock_find_range(start, end, size, align, nid);
> +		if (ret)
> +			return ret;
>  
> -		cand = round_down(this_end - size, align);
> -		if (cand >= this_start)
> -			return cand;
> +		pr_warn("memblock: Failed to allocate memory in bottom up direction. Now try top down direction.\n");

Is there any chance that this retry will succeed given that start and
end are still the same?

Thanks,
-Toshi


>  	}
> -	return 0;
> +
> +	return __memblock_find_range_rev(start, end, size, align, nid);
>  }
>  
>  /**


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