On Thu, Jun 21, 2012 at 6:47 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> I'm afraid this is too early.  We don't want the region to be unmapped
>> yet.  This should only happen after all memblock usages are finished
>> which I don't think is the case yet.
>
> No, it is not early. at that time memblock usage is done.
>
> Also I tested one system with huge memory, duplicated the problem on
> KVM that Sasha met.
> my patch fixes the problem.
>
> please check attached patch.
>
> Also I add another patch to double check if there is any reference
> with reserved.region.
> so far there is no reference found.

please check attached boot log.

free list before patch:
[    0.000000]        [0x1017a00000-0x1017ebdfff]
[    0.000000]        [0x101f7fb000-0x101fbcffff]
[    0.000000]        [0x101fbd6000-0x101fe5cfff]
[    0.000000]        [0x101fec6000-0x101fec8fff]
[    0.000000] BUG: unable to handle kernel paging request at ffff88101fec7748
[    0.000000] IP: [<ffffffff81d989c8>] __next_free_mem_range+0xdc/0x181

free list after patch:
[    0.000000]        [0x1017a00000-0x1017ebdfff]
[    0.000000]        [0x101f7fb000-0x101fbcffff]
[    0.000000]        [0x101fbd6000-0x101fe5cfff]
[    0.000000]        [0x101fec8000-0x101fec8fff]
[    0.000000]        [0x101fecb000-0x101fecafff]
[    0.000000]        [0x101fecd000-0x101feccfff]
[    0.000000]        [0x101fec5000-0x101fec7fff]

some kind of moving _pa(reserved.region) free to the last.

Thanks

Yinghai