linux-kernel - Re: [PATCH 06/10] bootmem: refactor free_all_bootmem

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Date:	Wed, 28 Oct 2009 08:36:45 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	linux-kernel@...r.kernel.org, chrisw@...s-sol.org,
	dwmw2@...radead.org, joerg.roedel@....com
Subject: Re: [PATCH 06/10] bootmem: refactor free_all_bootmem_core


* FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> wrote:

> From: Chris Wright <chrisw@...s-sol.org>
> 
> Move the loop that frees all bootmem pages back to page allocator into
> its own function.  This should have not functional effect and allows the
> function to be reused later.
> 
> Reviewed-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> Signed-off-by: Chris Wright <chrisw@...s-sol.org>
> ---
>  mm/bootmem.c |   61 +++++++++++++++++++++++++++++++++++++++-------------------
>  1 files changed, 41 insertions(+), 20 deletions(-)
> 
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 555d5d2..94ef2e7 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -143,17 +143,22 @@ unsigned long __init init_bootmem(unsigned long start, unsigned long pages)
>  	return init_bootmem_core(NODE_DATA(0)->bdata, start, 0, pages);
>  }
>  
> -static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
> +/**
> + * free_bootmem_pages - frees bootmem pages to page allocator
> + * @start: start pfn
> + * @end: end pfn
> + * @map: bootmem bitmap of reserved pages
> + *
> + * This will free the pages in the range @start to @end, making them
> + * available to the page allocator.  The @map will be used to skip
> + * reserved pages.  Returns the count of pages freed.
> + */
> +static unsigned long __init free_bootmem_pages(unsigned long start,
> +					       unsigned long end,
> +					       unsigned long *map)
>  {
> +	unsigned long cursor, count = 0;
>  	int aligned;
> -	struct page *page;
> -	unsigned long start, end, pages, count = 0;
> -
> -	if (!bdata->node_bootmem_map)
> -		return 0;
> -
> -	start = bdata->node_min_pfn;
> -	end = bdata->node_low_pfn;
>  
>  	/*
>  	 * If the start is aligned to the machines wordsize, we might
> @@ -161,27 +166,25 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
>  	 */
>  	aligned = !(start & (BITS_PER_LONG - 1));
>  
> -	bdebug("nid=%td start=%lx end=%lx aligned=%d\n",
> -		bdata - bootmem_node_data, start, end, aligned);
> +	for (cursor = start; cursor < end; cursor += BITS_PER_LONG) {
> +		unsigned long idx, vec;
>  
> -	while (start < end) {
> -		unsigned long *map, idx, vec;
> -
> -		map = bdata->node_bootmem_map;
> -		idx = start - bdata->node_min_pfn;
> +		idx = cursor - start;
>  		vec = ~map[idx / BITS_PER_LONG];
>  
> -		if (aligned && vec == ~0UL && start + BITS_PER_LONG < end) {
> +		if (aligned && vec == ~0UL && cursor + BITS_PER_LONG < end) {
>  			int order = ilog2(BITS_PER_LONG);
>  
> -			__free_pages_bootmem(pfn_to_page(start), order);
> +			__free_pages_bootmem(pfn_to_page(cursor), order);
>  			count += BITS_PER_LONG;
>  		} else {
>  			unsigned long off = 0;
>  
>  			while (vec && off < BITS_PER_LONG) {
>  				if (vec & 1) {
> -					page = pfn_to_page(start + off);
> +					struct page *page;
> +
> +					page = pfn_to_page(cursor + off);
>  					__free_pages_bootmem(page, 0);
>  					count++;
>  				}
> @@ -189,8 +192,26 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
>  				off++;
>  			}
>  		}
> -		start += BITS_PER_LONG;
>  	}
> +	return count;
> +}
> +
> +static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
> +{
> +	struct page *page;
> +	unsigned long start, end, *map, pages, count = 0;
> +
> +	if (!bdata->node_bootmem_map)
> +		return 0;
> +
> +	start = bdata->node_min_pfn;
> +	end = bdata->node_low_pfn;
> +	map = bdata->node_bootmem_map;
> +
> +	bdebug("nid=%td start=%lx end=%lx\n", bdata - bootmem_node_data,
> +		start, end);
> +
> +	count = free_bootmem_pages(start, end, map);
>  
>  	page = virt_to_page(bdata->node_bootmem_map);
>  	pages = bdata->node_low_pfn - bdata->node_min_pfn;

Small nit: the initialization of count to 0 seems superfluous.

	Ingo
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