[PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
ard.biesheuvel at linaro.org
Wed Jan 4 05:50:20 PST 2017
On 4 January 2017 at 13:28, Will Deacon <will.deacon at arm.com> wrote:
> On Wed, Dec 14, 2016 at 09:11:47AM +0000, Ard Biesheuvel wrote:
>> The NUMA code may get confused by the presence of NOMAP regions within
>> zones, resulting in spurious BUG() checks where the node id deviates
>> from the containing zone's node id.
>> Since the kernel has no business reasoning about node ids of pages it
>> does not own in the first place, enable CONFIG_HOLES_IN_ZONE to ensure
>> that such pages are disregarded.
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> arch/arm64/Kconfig | 4 ++++
>> 1 file changed, 4 insertions(+)
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 111742126897..0472afe64d55 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -614,6 +614,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>> def_bool y
>> depends on NUMA
>> +config HOLES_IN_ZONE
>> + def_bool y
>> + depends on NUMA
>> source kernel/Kconfig.preempt
>> source kernel/Kconfig.hz
> I'm happy to apply this, but I'll hold off until the first patch is queued
> somewhere, since this doesn't help without the VM_BUG_ON being moved.
> Alternatively, I can queue both if somebody from the mm camp acks the
> first patch.
Actually, I am not convinced the discussion is finalized. These
patches do fix the issue, but Robert also suggested an alternative fix
which may be preferable.
I haven't responded to it yet, due to the holidays, but I'd like to
explore that solution a bit further before applying anything, if you
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