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Subject: Re: [PATCH v2 1/7] mm/hotplug: fix hot remove failure in
 SPARSEMEM|!VMEMMAP case
To:     Baoquan He <bhe@redhat.com>, linux-kernel@vger.kernel.org
Cc:     linux-mm@kvack.org, akpm@linux-foundation.org,
        richardw.yang@linux.intel.com, osalvador@suse.de,
        dan.j.williams@intel.com, mhocko@suse.com, rppt@linux.ibm.com,
        robin.murphy@arm.com
References: <20200220043316.19668-1-bhe@redhat.com>
 <20200220043316.19668-2-bhe@redhat.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <4535ac89-3ece-a665-dbe6-ea766a618135@redhat.com>
Date:   Thu, 20 Feb 2020 13:07:07 +0100
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On 20.02.20 05:33, Baoquan He wrote:
> In section_deactivate(), pfn_to_page() doesn't work any more after
> ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case.
> It caused hot remove failure:
> 
> kernel BUG at mm/page_alloc.c:4806!
> invalid opcode: 0000 [#1] SMP PTI
> CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> RIP: 0010:free_pages+0x85/0xa0
> Call Trace:
>  __remove_pages+0x99/0xc0
>  arch_remove_memory+0x23/0x4d
>  try_remove_memory+0xc8/0x130
>  ? walk_memory_blocks+0x72/0xa0
>  __remove_memory+0xa/0x11
>  acpi_memory_device_remove+0x72/0x100
>  acpi_bus_trim+0x55/0x90
>  acpi_device_hotplug+0x2eb/0x3d0
>  acpi_hotplug_work_fn+0x1a/0x30
>  process_one_work+0x1a7/0x370
>  worker_thread+0x30/0x380
>  ? flush_rcu_work+0x30/0x30
>  kthread+0x112/0x130
>  ? kthread_create_on_node+0x60/0x60
>  ret_from_fork+0x35/0x40
> 
> Let's move the ->section_mem_map resetting after depopulate_section_memmap()
> to fix it.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb