linux-kernel - Re: [PATCH v2] kexec: Make a pair of map and unmap reserved pages when kdump fails to start

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Message-ID: <20150701150650.GA11010@huangminfeis-MacBook-Pro.local>
Date:	Wed, 1 Jul 2015 23:06:50 +0800
From:	Minfei Huang <mnfhuang@...il.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Cc:	ebiederm@...ssion.com, vgoyal@...hat.com, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, linux390@...ibm.com,
	linux-s390@...r.kernel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kexec: Make a pair of map and unmap reserved pages
 when kdump fails to start

On 07/01/15 at 04:40P, Michael Holzheu wrote:
> Hello Minfei,
> 
> Regarding functionality your patch looks ok for me.
> But the code is not easy to read.
> 
> What about replacing the "failure" label with "fail_unmap_pages"?

Sure. I will repost v3 to fix it.

Thanks
Minfei

> 
> Michael
> 
> On Tue, 30 Jun 2015 13:44:46 +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.
> > 
> > Now kexec will never unmap the reserved pages, once it fails to continue
> > starting the kdump service.
> > 
> > Make a pair of reserved pages in kdump starting path, whatever kexec
> > fails or not.
> > 
> > Signed-off-by: Minfei Huang <mnfhuang@...il.com>
> > ---
> >  kernel/kexec.c | 26 ++++++++++++++------------
> >  1 file changed, 14 insertions(+), 12 deletions(-)
> > 
> > diff --git a/kernel/kexec.c b/kernel/kexec.c
> > index 4589899..68f6dfb 100644
> > --- a/kernel/kexec.c
> > +++ b/kernel/kexec.c
> > @@ -1291,35 +1291,37 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
> >  			 */
> > 
> >  			kimage_free(xchg(&kexec_crash_image, NULL));
> > -			result = kimage_alloc_init(&image, entry, nr_segments,
> > -						   segments, flags);
> > -			crash_map_reserved_pages();
> > -		} else {
> > -			/* Loading another kernel to reboot into. */
> > -
> > -			result = kimage_alloc_init(&image, entry, nr_segments,
> > -						   segments, flags);
> >  		}
> > +
> > +		result = kimage_alloc_init(&image, entry, nr_segments,
> > +				segments, flags);
> >  		if (result)
> >  			goto out;
> > 
> > +		if (flags & KEXEC_ON_CRASH)
> > +			crash_map_reserved_pages();
> > +
> >  		if (flags & KEXEC_PRESERVE_CONTEXT)
> >  			image->preserve_context = 1;
> >  		result = machine_kexec_prepare(image);
> >  		if (result)
> > -			goto out;
> > +			goto failure;
> > 
> >  		for (i = 0; i < nr_segments; i++) {
> >  			result = kimage_load_segment(image, &image->segment[i]);
> >  			if (result)
> > -				goto out;
> > +				goto failure;
> >  		}
> >  		kimage_terminate(image);
> > +
> > +failure:
> >  		if (flags & KEXEC_ON_CRASH)
> >  			crash_unmap_reserved_pages();
> >  	}
> > -	/* Install the new kernel, and  Uninstall the old */
> > -	image = xchg(dest_image, image);
> > +
> > +	if (result == 0)
> > +		/* Install the new kernel, and  Uninstall the old */
> > +		image = xchg(dest_image, image);
> > 
> >  out:
> >  	mutex_unlock(&kexec_mutex);
> 
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