linux-kernel - Re: [PATCH 07/10] bootmem: add free_bootmem

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Message-ID: <84144f020911091213j393a9761pe13808d1e091e169@mail.gmail.com>
Date:	Mon, 9 Nov 2009 22:13:40 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	linux-kernel@...r.kernel.org, chrisw@...s-sol.org,
	dwmw2@...radead.org, joerg.roedel@....com, mingo@...e.hu,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 07/10] bootmem: add free_bootmem_late

On Wed, Oct 28, 2009 at 8:47 AM, FUJITA Tomonori
<fujita.tomonori@....ntt.co.jp> wrote:
> @@ -151,7 +151,9 @@ unsigned long __init init_bootmem(unsigned long start, unsigned long 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.
> + * reserved pages.  In the case that @map is NULL, the bootmem allocator
> + * is already free and the range is contiguous.  Returns the count of
> + * pages freed.
>  */
>  static unsigned long __init free_bootmem_pages(unsigned long start,
>                                               unsigned long end,
> @@ -164,13 +166,23 @@ static unsigned long __init free_bootmem_pages(unsigned long start,
>         * If the start is aligned to the machines wordsize, we might
>         * be able to free pages in bulks of that order.
>         */
> -       aligned = !(start & (BITS_PER_LONG - 1));
> +       if (map)
> +               aligned = !(start & (BITS_PER_LONG - 1));
> +       else
> +               aligned = 1;

Why do we need this special casing here? Isn't start always aligned
properly for callers with map == NULL?

>
>        for (cursor = start; cursor < end; cursor += BITS_PER_LONG) {
> -               unsigned long idx, vec;
> +               unsigned long vec;
>
> -               idx = cursor - start;
> -               vec = ~map[idx / BITS_PER_LONG];
> +               if (map) {
> +                       unsigned long idx = cursor - start;
> +                       vec = ~map[idx / BITS_PER_LONG];
> +               } else {
> +                       if (end - cursor >= BITS_PER_LONG)
> +                               vec = ~0UL;

Why do we need the above?

> +                       else
> +                               vec = (1UL << (end - cursor)) - 1;
> +               }
>
>                if (aligned && vec == ~0UL && cursor + BITS_PER_LONG < end) {
>                        int order = ilog2(BITS_PER_LONG);
> @@ -387,6 +399,27 @@ void __init free_bootmem(unsigned long addr, unsigned long size)
>  }
>
>  /**
> + * free_bootmem_late - free bootmem pages directly to page allocator
> + * @addr: starting address of the range
> + * @size: size of the range in bytes
> + *
> + * This is only useful when the bootmem allocator has already been torn
> + * down, but we are still initializing the system.  Pages are given directly
> + * to the page allocator, no bootmem metadata is updated because it is gone.
> + */
> +void __init free_bootmem_late(unsigned long addr, unsigned long size)
> +{
> +       unsigned long start, end;
> +
> +       kmemleak_free_part(__va(addr), size);
> +
> +       start = PFN_UP(addr);
> +       end = PFN_DOWN(addr + size);
> +
> +       totalram_pages += free_bootmem_pages(start, end, NULL);
> +}
> +
> +/**
>  * reserve_bootmem_node - mark a page range as reserved
>  * @pgdat: node the range resides on
>  * @physaddr: starting address of the range
> --
> 1.5.6.5
>
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