Re: [PATCH v3 2/2] mm/page_alloc: fix memmap_init_zone pageblock alignment

[Naresh Kamboju]

On 12 March 2018 at 17:56, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> Hi,
>
> I couldn't find the exact mail corresponding to the patch merged in v4.16-rc5
> but commit 864b75f9d6b01 "mm/page_alloc: fix memmap_init_zone
> pageblock alignment"
> cause boot hang on my ARM64 platform.

I have also noticed this problem on hi6220 Hikey - arm64.

LKFT: linux-next: Hikey boot failed linux-next-20180308
https://bugs.linaro.org/show_bug.cgi?id=3676

- Naresh

>
> Log:
> [    0.000000] NUMA: No NUMA configuration found
> [    0.000000] NUMA: Faking a node at [mem
> 0x0000000000000000-0x00000009ffffffff]
> [    0.000000] NUMA: NODE_DATA [mem 0x9fffcb480-0x9fffccf7f]
> [    0.000000] Zone ranges:
> [    0.000000]   DMA32    [mem 0x0000000080000000-0x00000000ffffffff]
> [    0.000000]   Normal   [mem 0x0000000100000000-0x00000009ffffffff]
> [    0.000000] Movable zone start for each node
> [    0.000000] Early memory node ranges
> [    0.000000]   node   0: [mem 0x0000000080000000-0x00000000f8f9afff]
> [    0.000000]   node   0: [mem 0x00000000f8f9b000-0x00000000f908ffff]
> [    0.000000]   node   0: [mem 0x00000000f9090000-0x00000000f914ffff]
> [    0.000000]   node   0: [mem 0x00000000f9150000-0x00000000f920ffff]
> [    0.000000]   node   0: [mem 0x00000000f9210000-0x00000000f922ffff]
> [    0.000000]   node   0: [mem 0x00000000f9230000-0x00000000f95bffff]
> [    0.000000]   node   0: [mem 0x00000000f95c0000-0x00000000fe58ffff]
> [    0.000000]   node   0: [mem 0x00000000fe590000-0x00000000fe5cffff]
> [    0.000000]   node   0: [mem 0x00000000fe5d0000-0x00000000fe5dffff]
> [    0.000000]   node   0: [mem 0x00000000fe5e0000-0x00000000fe62ffff]
> [    0.000000]   node   0: [mem 0x00000000fe630000-0x00000000feffffff]
> [    0.000000]   node   0: [mem 0x0000000880000000-0x00000009ffffffff]
> [    0.000000]  Initmem setup node 0 [mem 0x0000000080000000-0x00000009ffffffff]
>
> On Sat, Mar 3, 2018 at 1:08 AM, Daniel Vacek <neelx@xxxxxxxxxx> wrote:
>> On Sat, Mar 3, 2018 at 1:40 AM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>>> On Sat,  3 Mar 2018 01:12:26 +0100 Daniel Vacek <neelx@xxxxxxxxxx> wrote:
>>>
>>>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>>>> where possible") introduced a bug where move_freepages() triggers a
>>>> VM_BUG_ON() on uninitialized page structure due to pageblock alignment.
>>>
>>> b92df1de5d28 was merged a year ago.  Can you suggest why this hasn't
>>> been reported before now?
>>
>> Yeah. I was surprised myself I couldn't find a fix to backport to
>> RHEL. But actually customers started to report this as soon as 7.4
>> (where b92df1de5d28 was merged in RHEL) was released. I remember
>> reports from September/October-ish times. It's not easily reproduced
>> and happens on a handful of machines only. I guess that's why. But
>> that does not make it less serious, I think.
>>
>> Though there actually is a report here:
>> https://bugzilla.kernel.org/show_bug.cgi?id=196443
>>
>> And there are reports for Fedora from July:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1473242
>> and CentOS: https://bugs.centos.org/view.php?id=13964
>> and we internally track several dozens reports for RHEL bug
>> https://bugzilla.redhat.com/show_bug.cgi?id=1525121
>>
>> Enough? ;-)
>>
>>> This makes me wonder whether a -stable backport is really needed...
>>
>> For some machines it definitely is. Won't hurt either, IMHO.
>>
>> --nX