linux-kernel - Re: [PATCH v2] kdump: crashk_res init check for /sys/kernel/kexec_crash

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Date:	Wed, 23 Nov 2011 23:01:00 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	holzheu@...ux.vnet.ibm.com
Cc:	akpm@...ux-foundation.org, Simon Horman <horms@...ge.net.au>,
	heiko.carstens@...ibm.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	schwidefsky@...ibm.com, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH v2] kdump: crashk_res init check for /sys/kernel/kexec_crash_size

On Wed, Nov 23, 2011 at 9:18 PM, Michael Holzheu
<holzheu@...ux.vnet.ibm.com> wrote:
> From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
>
> Currently it is possible to set the crash_size via the sysfs
> /sys/kernel/kexec_crash_size even if no crash kernel memory has
> been defined with the "crashkernel" parameter. In this case
> "crashk_res" is not initialized and crashk_res.start = crashk_res.end = 0.
> Unfortunately resource_size(&crashk_res) returns 1 in this case.
> This breaks the s390 implementation of crash_(un)map_reserved_pages().
>
> To fix the problem the correct "old_size" is now calculated in
> crash_shrink_memory(). "old_size is set to "0" if crashk_res is
> not initialized. With this change crash_shrink_memory() will do nothing,
> when "crashk_res" is not initialized. It will return "0" for
> "echo 0 > /sys/kernel/kexec_crash_size" and -EINVAL for
> "echo [not zero] > /sys/kernel/kexec_crash_size".
>
> In addition to that this patch also simplifies the "ret = -EINVAL"
> vs. "ret = 0" logic as suggested by Simon Horman.
>
> Cc: Simon Horman <horms@...ge.net.au>
> Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>

Reviewed-by: WANG Cong <xiyou.wangcong@...il.com>

Thanks.
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