linux-kernel - Re: [PATCH 04/13] vmcore: introduce types for objects copied in 2nd kernel

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Date:	Tue, 19 Feb 2013 01:06:31 +0900 (JST)
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	vgoyal@...hat.com
Cc:	ebiederm@...ssion.com, cpw@....com,
	kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/13] vmcore: introduce types for objects copied in
 2nd kernel

From: Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH 04/13] vmcore: introduce types for objects copied in 2nd kernel
Date: Fri, 15 Feb 2013 10:28:28 -0500

> On Thu, Feb 14, 2013 at 07:12:05PM +0900, HATAYAMA Daisuke wrote:
>> Some parts of old memory need to be copied in buffers on 2nd kernel to
>> be remapped to user-space. To distinguish objects in the buffer on 2nd
>> kernel and the ones on old memory, enum vmcore_type is introduced: the
>> object in the buffer on 2nd kernel has VMCORE_2ND_KERNEL type, and the
>> one on old memory has VMCORE_OLD_MEMORY type.
>> 
>> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
>> ---
>> 
>>  include/linux/proc_fs.h |   11 ++++++++++-
>>  1 files changed, 10 insertions(+), 1 deletions(-)
>> 
>> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
>> index 32676b3..4b153ed 100644
>> --- a/include/linux/proc_fs.h
>> +++ b/include/linux/proc_fs.h
>> @@ -97,11 +97,20 @@ struct kcore_list {
>>  	int type;
>>  };
>>  
>> +enum vmcore_type {
>> +	VMCORE_OLD_MEMORY,
>> +	VMCORE_2ND_KERNEL,
> 
> This VMCORE_2ND_KERNEL tag looks bad.
> 
> How about introducing a "unsigned int flag" element in "struct vmcore"
> and set the flag MEM_TYPE_OLDMEM for any contents which come from oldmem.
> 
> If MEM_TYPE_OLDMEM is not set, it is assumed that contents are to be
> fetched from current kernel using pointer vmcore->buf.

This sounds strange to me. There has not been contents to be fetched
from current kenrel so far. So, object with MEM_TYPE_OLDMEM seems more
normal than without. Should we prepare special type for objects in 2nd
kernel?

Thanks.
HATAYAMA, Daisuke

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