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

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: David Hildenbrand <david@redhat.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 16:06:02 +0530	[thread overview]
Message-ID: <dbaec657-db02-d721-0288-c8b8b727153d@linux.ibm.com> (raw)
In-Reply-To: <e3217688-0f58-f922-01d4-f19001bb23ad@redhat.com>

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.

-aneesh
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