linux-kernel - Re: [PATCH 6/7] mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM

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Date:   Mon, 10 Feb 2020 11:45:31 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, richardw.yang@...ux.intel.com,
        david@...hat.com
Subject: Re: [PATCH 6/7] mm/sparsemem: pfn_to_page is not valid yet on
 SPARSEMEM

On 02/09/20 at 06:48pm, Baoquan He wrote:
> From: Wei Yang <richardw.yang@...ux.intel.com>
> 
> When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page()
> doesn't work before sparse_init_one_section() is called. This leads to a
> crash when hotplug memory.
> 
> PGD 0 P4D 0
> Oops: 0002 [#1] SMP PTI
> CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #339
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> RIP: 0010:__memset+0x24/0x30
> Call Trace:
>  sparse_add_section+0x150/0x1d8
>  __add_pages+0xbf/0x150
>  add_pages+0x12/0x60
>  add_memory_resource+0xc8/0x210
>  ? wake_up_q+0xa0/0xa0
>  __add_memory+0x62/0xb0
>  acpi_memory_device_add+0x13f/0x300
>  acpi_bus_attach+0xf6/0x200
>  acpi_bus_scan+0x43/0x90
>  acpi_device_hotplug+0x275/0x3d0
>  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
> 
> We should use memmap as it did.
> 
> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Reviewed-by: Baoquan He <bhe@...hat.com>
> CC: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Baoquan He <bhe@...hat.com>

Git format-patch added this line of Signed-off-by from me, I will
remove it if repost.

> ---
>  mm/sparse.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index a7e78bfe0dce..623755e88255 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -944,7 +944,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>  	 * Poison uninitialized struct pages in order to catch invalid flags
>  	 * combinations.
>  	 */
> -	page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
> +	page_init_poison(memmap, sizeof(struct page) * nr_pages);
>  
>  	ms = __nr_to_section(section_nr);
>  	set_section_nid(section_nr, nid);
> -- 
> 2.17.2
>