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 12:40:03 +0200	[thread overview]
Message-ID: <59f15b2c-752b-68b1-30bd-f25386737a59@redhat.com> (raw)
In-Reply-To: <dbaec657-db02-d721-0288-c8b8b727153d@linux.ibm.com>

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).

Is there a Fixes: Tag we can add to the first patch?

-- 

Thanks,

David / dhildenb
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