Re: [PATCH] makedumpfile: fix max_mapnr issue on system has over 44-bit addressing

From: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
To: Jingbai Ma <jingbai.ma@hp.com>
Cc: bhe@redhat.com, nishimura@mxp.nes.nec.co.jp,
	usui@mxm.nes.nec.co.jp, lisa.mitchell@hp.com, ruyang@redhat.com,
	tachibana@mxm.nes.nec.co.jp, anderson@redhat.com,
	chaowang@redhat.com, kumagai-atsushi@mxc.nes.nec.co.jp,
	kexec@lists.infradead.org, vgoyal@redhat.com,
	crash-utility@redhat.com
Subject: Re: [PATCH] makedumpfile: fix max_mapnr issue on system has over 44-bit addressing
Date: Wed, 25 Sep 2013 17:39:23 +0900	[thread overview]
Message-ID: <5242A13B.6000907@jp.fujitsu.com> (raw)
In-Reply-To: <52429BF1.3050303@hp.com>

(2013/09/25 17:16), Jingbai Ma wrote:
<cut>
>>
>>> @@ -5153,10 +5160,11 @@ write_kdump_header(void)
>>> * Write common header
>>> */
>>> strncpy(dh->signature, KDUMP_SIGNATURE, strlen(KDUMP_SIGNATURE));
>>> - dh->header_version = 5;
>>> + dh->header_version = 6;
>>> dh->block_size = info->page_size;
>>> dh->sub_hdr_size = sizeof(kh) + size_note;
>>> dh->sub_hdr_size = divideup(dh->sub_hdr_size, dh->block_size);
>>> + /* dh->max_mapnr may be truncated here, full 64bit in kh.max_mapnr */
>>> dh->max_mapnr = info->max_mapnr;
>>
>> dh->max_mapnr = MIN(info->max_mapnr, UINT_MAX) seems better for old
>> versions of crash utitlity.
>>
>
> Although change this value to UINT_MAX doesn't help the old crash utility very much. At least this special value will tell the user something happened.
> Will fix it.
>
>

This is the largest page frame number old crash utilities can represent, not special value.
By this, old crash utilities can read at least the pages less than UINT_MAX,
which is better than making dh->max_mapnr overflow; then dh->max_mapnr would typically become
a small number.

-- 
Thanks.
HATAYAMA, Daisuke

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec