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 at 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 at verge.net.au>
>>> Signed-off-by: Michael Holzheu <holzheu at 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 at 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
