linux-kernel - Re: [Patch 8/8] kexec: allow to shrink reserved memory

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Date:	Wed, 19 Aug 2009 10:41:13 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	linux-ia64@...r.kernel.org, linux-mm@...ck.org,
	Neil Horman <nhorman@...hat.com>,
	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	bernhard.walle@....de, Fenghua Yu <fenghua.yu@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Anton Vorontsov <avorontsov@...mvista.com>
Subject: Re: [Patch 8/8] kexec: allow to shrink reserved memory

KAMEZAWA Hiroyuki wrote:
> On Tue, 18 Aug 2009 18:35:32 +0800
> Amerigo Wang <amwang@...hat.com> wrote:
>
>   
>> KAMEZAWA Hiroyuki wrote:
>>     
>>> On Tue, 18 Aug 2009 14:31:23 +0800
>>> Amerigo Wang <amwang@...hat.com> wrote:
>>>   
>>>       
>>>>>     It's hidden from the system before mem_init() ?
>>>>>   
>>>>>       
>>>>>           
>>>> Not sure, but probably yes. It is reserved in setup_arch() which is 
>>>> before mm_init() which calls mem_init().
>>>>
>>>> Do you have any advice to free that reserved memory after boot? :)
>>>>
>>>>     
>>>>         
>>> Let's see arch/x86/mm/init.c::free_initmem()
>>>
>>> Maybe it's all you want.
>>>
>>> 	- ClearPageReserved()
>>> 	- init_page_count()
>>> 	- free_page()
>>> 	- totalram_pages++
>>>   
>>>       
>> Just FYI: calling ClearPageReserved() caused an oops: "Unable to handle 
>> paging request".
>>
>> I am trying to figure out why...
>>
>>     
> Hmm...then....memmap is not there.
> pfn_valid() check will help you. What arch ? x86-64 ?
>   

Hmm, yes, x86_64, but this code is arch-independent, I mean it should 
work or not work on all arch, no?

So I am afraid we need to use other API to free it...

Thanks.


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