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Re: [PATCH] [MIPS] Hibernation: only save pages in system ram

To: Wu Zhangjin <wuzhangjin@gmail.com>
Subject: Re: [PATCH] [MIPS] Hibernation: only save pages in system ram
From: "Rafael J. Wysocki" <rjw@sisk.pl>
Date: Fri, 3 Jul 2009 01:22:40 +0200
Cc: LKML <linux-kernel@vger.kernel.org>, linux-mips@linux-mips.org, Pavel Machek <pavel@ucw.cz>, Ralf Baechle <ralf@linux-mips.org>, Wu Zhangjin <wuzj@lemote.com>
In-reply-to: <1246373570-21090-1-git-send-email-wuzhangjin@gmail.com>
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On Tuesday 30 June 2009, Wu Zhangjin wrote:
> From: Wu Zhangjin <wuzj@lemote.com>
> 
> when using hibernation(STD) with CONFIG_FLATMEM in linux-mips-64bit, it
> fails for the current mips-specific hibernation implementation save the
> pages in all of the memory space(except the nosave section) and make
> there will be not enough memory left to the STD task itself, and then
> fail. in reality, we only need to save the pages in system rams.
> 
> here is the reason why it fail:
> 
> kernel/power/snapshot.c:
> 
> static void mark_nosave_pages(struct memory_bitmap *bm)
> {
>               ...
>               if (pfn_valid(pfn)) {
>                       ...
>               }
> }
> 
> arch/mips/include/asm/page.h:
> 
>       ...
>       #ifdef CONFIG_FLATMEM
> 
>       #define pfn_valid(pfn)          ((pfn) >= ARCH_PFN_OFFSET && (pfn) < 
> max_mapnr)
> 
>       #elif defined(CONFIG_SPARSEMEM)
> 
>       /* pfn_valid is defined in linux/mmzone.h */
>       ...
> 
> we can rewrite pfn_valid(pfn) to fix this problem, but I really do not
> want to touch such a widely-used macro, so, I used another solution:
> 
> static struct page *saveable_page(struct zone *zone, unsigned long pfn)
> {
>       ...
>       if ( .... pfn_is_nosave(pfn)
>               return NULL;
>       ...
> }
> 
> and pfn_is_nosave is implemented in arch/mips/power/cpu.c, so, hacking
> this one is better.

Not really.

Could that be handled with the help of register_nosave_region() or
register_nosave_region_late() instead?

Best,
Rafael


> Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
> ---
>  arch/mips/power/cpu.c |   19 ++++++++++++++++++-
>  1 files changed, 18 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/mips/power/cpu.c b/arch/mips/power/cpu.c
> index 7995df4..ef472e3 100644
> --- a/arch/mips/power/cpu.c
> +++ b/arch/mips/power/cpu.c
> @@ -10,6 +10,7 @@
>  #include <asm/suspend.h>
>  #include <asm/fpu.h>
>  #include <asm/dsp.h>
> +#include <asm/bootinfo.h>
>  
>  static u32 saved_status;
>  struct pt_regs saved_regs;
> @@ -34,10 +35,26 @@ void restore_processor_state(void)
>               restore_dsp(current);
>  }
>  
> +int pfn_in_system_ram(unsigned long pfn)
> +{
> +     int i;
> +
> +     for (i = 0; i < boot_mem_map.nr_map; i++) {
> +             if (boot_mem_map.map[i].type == BOOT_MEM_RAM) {
> +                     if ((pfn >= (boot_mem_map.map[i].addr >> PAGE_SHIFT)) &&
> +                             ((pfn) < ((boot_mem_map.map[i].addr +
> +                                     boot_mem_map.map[i].size) >> 
> PAGE_SHIFT)))
> +                             return 1;
> +             }
> +     }
> +     return 0;
> +}
> +
>  int pfn_is_nosave(unsigned long pfn)
>  {
>       unsigned long nosave_begin_pfn = PFN_DOWN(__pa(&__nosave_begin));
>       unsigned long nosave_end_pfn = PFN_UP(__pa(&__nosave_end));
>  
> -     return  (pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn);
> +     return ((pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn))
> +                     || !pfn_in_system_ram(pfn);
>  }

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