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

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Date:	Wed, 1 Jul 2015 16:40:23 +0200
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Minfei Huang <mnfhuang@...il.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

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"?

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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