linux-kernel - Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel to speedup kernel dump process

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Date:	Fri, 08 Mar 2013 08:19:09 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Jingbai Ma <jingbai.ma@...com>, mingo@...hat.com,
	kumagai-atsushi@....nes.nec.co.jp, hpa@...or.com,
	yinghai@...nel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/5] crash dump bitmap: scan memory pages in kernel to speedup kernel dump process

Vivek Goyal <vgoyal@...hat.com> writes:

> On Thu, Mar 07, 2013 at 01:54:45PM -0800, Eric W. Biederman wrote:
>> Vivek Goyal <vgoyal@...hat.com> writes:
>> > I think this is not a good idea. It has several issues.
>> 
>> Actually it does not appear to be doing any work in the first kernel.
>
> Looks like patch3 in series is doing that.
>
>                         machine_crash_shutdown(&fixed_regs);
> +                       generate_crash_dump_bitmap();
>                         machine_kexec(kexec_crash_image);
>
> So this bitmap seems to be being set just before transitioning into
> second kernel.
>
> I am sure you would not like this extra code in this path. :-)

Ouch!  I had totally missed that.  No that is not at all acceptable.

I was blind that day.  The only call I saw was in patch 4 that put
the call generated the bitmap in the new proc file.

Eric
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