From: Dave Young <dyoung@redhat.com>
To: holzheu@linux.vnet.ibm.com
Cc: heiko.carstens@de.ibm.com, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, Simon Horman <horms@verge.net.au>,
"Eric W. Biederman" <ebiederm@xmission.com>,
schwidefsky@de.ibm.com, akpm@linux-foundation.org,
Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH v2] kdump: crashk_res init check for /sys/kernel/kexec_crash_size
Date: Wed, 23 Nov 2011 22:03:10 +0800 [thread overview]
Message-ID: <4ECCFD1E.4030908@redhat.com> (raw)
In-Reply-To: <1322055976.10119.17.camel@br98xy6r>
On 11/23/2011 09:46 PM, Michael Holzheu wrote:
> Hi Dave,
>
> On Wed, 2011-11-23 at 21:34 +0800, Dave Young wrote:
>> On 11/23/2011 09:18 PM, Michael Holzheu wrote:
>>
>>> From: Michael Holzheu <holzheu@linux.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@verge.net.au>
>>> Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
>>> ---
>>> kernel/kexec.c | 10 ++++------
>>> 1 file changed, 4 insertions(+), 6 deletions(-)
>>>
>>> --- a/kernel/kexec.c
>>> +++ b/kernel/kexec.c
>>> @@ -1131,7 +1131,7 @@ void __weak crash_free_reserved_phys_ran
>>> int crash_shrink_memory(unsigned long new_size)
>>> {
>>> int ret = 0;
>>> - unsigned long start, end;
>>> + unsigned long start, end, old_size;
>>
>>
>> Sorry for jump in a little late, instead of introduce a new variable,
>> why not add something like:
>>
>> if (!end)
>> return -EINVAL;
>
> If the crashkernel parameter is not set, "/sys/kernel/kexec_crash_size"
> returns zero:
>
> cat /sys/kernel/kexec_crash_size
> 0
>
> So I think if we set it again to zero we should *not* return -EINVAL:
Thanks, I missed this case. fair enough.
Reviewed-by: Dave Young <dyoung@redhat.com>
>
> echo 0 > /sys/kernel/kexec_crash_size
> --> Exit code should be zero in this case
>
> Otherwise we would change the current behavior.
>
> And besides of that, I think introducing the "old_size" variable makes
> the code more readable.
>
> Michael
>
>
--
Thanks
Dave
next prev parent reply other threads:[~2011-11-23 14:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-23 10:11 [PATCH] kdump: crashk_res init check for /sys/kernel/kexec_crash_size Michael Holzheu
2011-11-23 10:22 ` Simon Horman
2011-11-23 13:18 ` [PATCH v2] " Michael Holzheu
2011-11-23 13:34 ` Dave Young
2011-11-23 13:46 ` Michael Holzheu
2011-11-23 14:03 ` Dave Young [this message]
2011-11-23 15:01 ` Cong Wang
2011-11-24 0:10 ` Simon Horman
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