Re: [PATCH 1/2] arm64: avoid alloc memory on offline node

[Hanjun Guo <guohanjun@huawei.com>]

On 2018/6/7 18:55, Michal Hocko wrote:
> On Wed 06-06-18 15:39:34, Bjorn Helgaas wrote:
>> [+cc akpm, linux-mm, linux-pci]
>>
>> On Wed, Jun 6, 2018 at 10:44 AM Will Deacon <will.deacon@arm.com> wrote:
>>>
>>> On Thu, May 31, 2018 at 08:14:38PM +0800, Xie XiuQi wrote:
>>>> A numa system may return node which is not online.
>>>> For example, a numa node:
>>>> 1) without memory
>>>> 2) NR_CPUS is very small, and the cpus on the node are not brought up
>>>>
>>>> In this situation, we use NUMA_NO_NODE to avoid oops.
>>>>
>>>> [   25.732905] Unable to handle kernel NULL pointer dereference at virtual address 00001988
>>>> [   25.740982] Mem abort info:
>>>> [   25.743762]   ESR = 0x96000005
>>>> [   25.746803]   Exception class = DABT (current EL), IL = 32 bits
>>>> [   25.752711]   SET = 0, FnV = 0
>>>> [   25.755751]   EA = 0, S1PTW = 0
>>>> [   25.758878] Data abort info:
>>>> [   25.761745]   ISV = 0, ISS = 0x00000005
>>>> [   25.765568]   CM = 0, WnR = 0
>>>> [   25.768521] [0000000000001988] user address but active_mm is swapper
>>>> [   25.774861] Internal error: Oops: 96000005 [#1] SMP
>>>> [   25.779724] Modules linked in:
>>>> [   25.782768] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc6-mpam+ #115
>>>> [   25.789714] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 EC UEFI Nemo 2.0 RC0 - B305 05/28/2018
>>>> [   25.798831] pstate: 80c00009 (Nzcv daif +PAN +UAO)
>>>> [   25.803612] pc : __alloc_pages_nodemask+0xf0/0xe70
>>>> [   25.808389] lr : __alloc_pages_nodemask+0x184/0xe70
>>>> [   25.813252] sp : ffff00000996f660
>>>> [   25.816553] x29: ffff00000996f660 x28: 0000000000000000
>>>> [   25.821852] x27: 00000000014012c0 x26: 0000000000000000
>>>> [   25.827150] x25: 0000000000000003 x24: ffff000008099eac
>>>> [   25.832449] x23: 0000000000400000 x22: 0000000000000000
>>>> [   25.837747] x21: 0000000000000001 x20: 0000000000000000
>>>> [   25.843045] x19: 0000000000400000 x18: 0000000000010e00
>>>> [   25.848343] x17: 000000000437f790 x16: 0000000000000020
>>>> [   25.853641] x15: 0000000000000000 x14: 6549435020524541
>>>> [   25.858939] x13: 20454d502067756c x12: 0000000000000000
>>>> [   25.864237] x11: ffff00000996f6f0 x10: 0000000000000006
>>>> [   25.869536] x9 : 00000000000012a4 x8 : ffff8023c000ff90
>>>> [   25.874834] x7 : 0000000000000000 x6 : ffff000008d73c08
>>>> [   25.880132] x5 : 0000000000000000 x4 : 0000000000000081
>>>> [   25.885430] x3 : 0000000000000000 x2 : 0000000000000000
>>>> [   25.890728] x1 : 0000000000000001 x0 : 0000000000001980
>>>> [   25.896027] Process swapper/0 (pid: 1, stack limit = 0x        (ptrval))
>>>> [   25.902712] Call trace:
>>>> [   25.905146]  __alloc_pages_nodemask+0xf0/0xe70
>>>> [   25.909577]  allocate_slab+0x94/0x590
>>>> [   25.913225]  new_slab+0x68/0xc8
>>>> [   25.916353]  ___slab_alloc+0x444/0x4f8
>>>> [   25.920088]  __slab_alloc+0x50/0x68
>>>> [   25.923562]  kmem_cache_alloc_node_trace+0xe8/0x230
>>>> [   25.928426]  pci_acpi_scan_root+0x94/0x278
>>>> [   25.932510]  acpi_pci_root_add+0x228/0x4b0
>>>> [   25.936593]  acpi_bus_attach+0x10c/0x218
>>>> [   25.940501]  acpi_bus_attach+0xac/0x218
>>>> [   25.944323]  acpi_bus_attach+0xac/0x218
>>>> [   25.948144]  acpi_bus_scan+0x5c/0xc0
>>>> [   25.951708]  acpi_scan_init+0xf8/0x254
>>>> [   25.955443]  acpi_init+0x310/0x37c
>>>> [   25.958831]  do_one_initcall+0x54/0x208
>>>> [   25.962653]  kernel_init_freeable+0x244/0x340
>>>> [   25.966999]  kernel_init+0x18/0x118
>>>> [   25.970474]  ret_from_fork+0x10/0x1c
>>>> [   25.974036] Code: 7100047f 321902a4 1a950095 b5000602 (b9400803)
>>>> [   25.980162] ---[ end trace 64f0893eb21ec283 ]---
>>>> [   25.984765] Kernel panic - not syncing: Fatal exception
>>>>
>>>> Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
>>>> Tested-by: Huiqiang Wang <wanghuiqiang@huawei.com>
>>>> Cc: Hanjun Guo <hanjun.guo@linaro.org>
>>>> Cc: Tomasz Nowicki <Tomasz.Nowicki@caviumnetworks.com>
>>>> Cc: Xishi Qiu <qiuxishi@huawei.com>
>>>> ---
>>>>  arch/arm64/kernel/pci.c | 3 +++
>>>>  1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
>>>> index 0e2ea1c..e17cc45 100644
>>>> --- a/arch/arm64/kernel/pci.c
>>>> +++ b/arch/arm64/kernel/pci.c
>>>> @@ -170,6 +170,9 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
>>>>       struct pci_bus *bus, *child;
>>>>       struct acpi_pci_root_ops *root_ops;
>>>>
>>>> +     if (node != NUMA_NO_NODE && !node_online(node))
>>>> +             node = NUMA_NO_NODE;
>>>> +
>>>
>>> This really feels like a bodge, but it does appear to be what other
>>> architectures do, so:
>>>
>>> Acked-by: Will Deacon <will.deacon@arm.com>
>>
>> I agree, this doesn't feel like something we should be avoiding in the
>> caller of kzalloc_node().
>>
>> I would not expect kzalloc_node() to return memory that's offline, no
>> matter what node we told it to allocate from.  I could imagine it
>> returning failure, or returning memory from a node that *is* online,
>> but returning a pointer to offline memory seems broken.
>>
>> Are we putting memory that's offline in the free list?  I don't know
>> where to look to figure this out.
> 
> I am not sure I have the full context but pci_acpi_scan_root calls
> kzalloc_node(sizeof(*info), GFP_KERNEL, node)
> and that should fall back to whatever node that is online. Offline node
> shouldn't keep any pages behind. So there must be something else going
> on here and the patch is not the right way to handle it. What does
> faddr2line __alloc_pages_nodemask+0xf0 tells on this kernel?

The whole context is:

The system is booted with a NUMA node has no memory attaching to it
(memory-less NUMA node), also with NR_CPUS less than CPUs presented
in MADT, so CPUs on this memory-less node are not brought up, and
this NUMA node will not be online (but SRAT presents this NUMA node);

Devices attaching to this NUMA node such as PCI host bridge still
return the valid NUMA node via _PXM, but actually that valid NUMA node
is not online which lead to this issue.

Thanks
Hanjun

>