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:
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
