linux-kernel - Re: [PATCH V2 1/2] kexec: Make a pair of map/unmap reserved pages in error path

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Message-ID: <20160302030320.GB20240@dhcp-128-25.nay.redhat.com>
Date:	Wed, 2 Mar 2016 11:03:20 +0800
From:	Minfei Huang <mhuang@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Minfei Huang <mnfhuang@...il.com>, ebiederm@...ssion.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] kexec: Make a pair of map/unmap reserved pages in
 error path

On 03/01/16 at 01:56pm, Andrew Morton wrote:
> On Tue,  1 Mar 2016 16:02:28 +0800 Minfei Huang <mnfhuang@...il.com> wrote:
> 
> > For some arch, kexec shall map the reserved pages, then use them, when
> > we try to start the kdump service.
> 
> Which architectures are these, by the way?

Hi.

This patch only affects s390. The others doesn't implement the interface
of crash_unmap_reserved_pages and crash_map_reserved_pages.

> 
> > kexec may return directly, without unmaping the reserved pages, if it
> > fails during starting service. To fix it, we make a pair of map/unmap
> > reserved pages both in generic path and error path.
> 
> I'm having trouble understanding the urgency of this patch.  Do you
> think it is needed in 4.5?  -stable?  If so, why?

IMHO, it is fine in next release as it isn't a urgent patch. Kernel can
work well without any risk, although the reseverd pages are not unmaped
before returning in error path.

Thanks
Minfei