Re: [PATCH 1/2] mm/memunmap: Use the correct start and end pfn when removing pages from zone

From: David Hildenbrand <david@redhat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-nvdimm@lists.01.org
Subject: Re: [PATCH 1/2] mm/memunmap: Use the correct start and end pfn when removing pages from zone
Date: Fri, 27 Sep 2019 13:38:48 +0200	[thread overview]
Message-ID: <71cdc35e-b9a5-d45f-9c02-a17eb9878da3@redhat.com> (raw)
In-Reply-To: <28ef81f4-13dc-db4c-f911-c4eb8be575cb@linux.ibm.com>

On 27.09.19 13:35, Aneesh Kumar K.V wrote:
> On 9/27/19 4:10 PM, David Hildenbrand wrote:
>> On 27.09.19 12:36, Aneesh Kumar K.V wrote:
>>> On 9/27/19 1:16 PM, David Hildenbrand wrote:
>>>> On 27.09.19 03:51, Aneesh Kumar K.V wrote:
>>>>> On 9/27/19 4:15 AM, Andrew Morton wrote:
>>>>>> On Thu, 26 Sep 2019 17:55:51 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:
>>>>>>
>>>>>>> With altmap, all the resource pfns are not initialized. While initializing
>>>>>>> pfn, altmap reserve space is skipped. Hence when removing pfn from zone skip
>>>>>>> pfns that were never initialized.
>>>>>>>
>>>>>>> Update memunmap_pages to calculate start and end pfn based on altmap
>>>>>>> values. This fixes a kernel crash that is observed when destroying namespace.
>>>>>>>
>>>>>>> [   74.745056] BUG: Unable to handle kernel data access at 0xc00c000001400000
>>>>>>> [   74.745256] Faulting instruction address: 0xc0000000000b58b0
>>>>>>> cpu 0x2: Vector: 300 (Data Access) at [c00000026ea93580]
>>>>>>>        pc: c0000000000b58b0: memset+0x68/0x104
>>>>>>>        lr: c0000000003eb008: page_init_poison+0x38/0x50
>>>>>>>        ...
>>>>>>>      current = 0xc000000271c67d80
>>>>>>>      paca    = 0xc00000003fffd680   irqmask: 0x03   irq_happened: 0x01
>>>>>>>        pid   = 3665, comm = ndctl
>>>>>>> [link register   ] c0000000003eb008 page_init_poison+0x38/0x50
>>>>>>> [c00000026ea93830] c0000000004754d4 remove_pfn_range_from_zone+0x64/0x3e0
>>>>>>> [c00000026ea938a0] c0000000004b8a60 memunmap_pages+0x300/0x400
>>>>>>> [c00000026ea93930] c0000000009e32a0 devm_action_release+0x30/0x50
>>>>>>
>>>>>> Doesn't apply to mainline or -next.  Which tree is this against?
>>>>>>
>>>>>
>>>>> After applying the patches from David on mainline. That is the reason I
>>>>> replied to this thread. I should have mentioned in the email that it is
>>>>> based on patch series "[PATCH v4 0/8] mm/memory_hotplug: Shrink zones
>>>>> before removing memory"
>>>>
>>>> So if I am not wrong, my patch "[PATCH v4 4/8] mm/memory_hotplug: Poison
>>>> memmap in remove_pfn_range_from_zone()" makes it show up that we
>>>> actually call _remove_pages() with wrong parameters, right?
>>>>
>>>> If so, I guess it would be better for you to fix it before my series and
>>>> I will rebase my series on top of that.
>>>>
>>>
>>> I posted a patch that can be applied to mainline. I sent that as a reply
>>> to this email. Can you include that and PATCH 2 as first two patches in
>>> your series?  That should help to locate the full patch series needed
>>> for fixing the kernel crash.
>>
>> I can drag these along, unless Andrew wants to pick them up right away
>> (or we're waiting for more feedback).
> 
> Considering this patch alone won't fix the issue, It would be nice if we 
> could club them with rest of the changes.
> 

I'll drag them along, adding Pankaj's RB's. If they get picked up
independently, fine :)

-- 

Thanks,

David / dhildenb
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