mm/huge_memory: use pfn_to_online_page() in split_huge_pages_all()

NULL pointer dereference is triggered when calling thp split via debugfs
on the system with offlined memory blocks.  With debug option enabled, the
following kernel messages are printed out:

  page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000
  flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff)
  raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000
  raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
  page dumped because: unmovable page
  page:000000007d7ab72e is uninitialized and poisoned
  page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
  ------------[ cut here ]------------
  kernel BUG at include/linux/mm.h:1248!
  invalid opcode: 0000 [#1] PREEMPT SMP PTI
  CPU: 16 PID: 20964 Comm: bash Tainted: G          I        6.0.0-rc3-foll-numa+ #41
  RIP: 0010:split_huge_pages_write+0xcf4/0xe30

This shows that page_to_nid() in page_zone() is unexpectedly called for an
offlined memmap.

Use pfn_to_online_page() to get struct page in PFN walker.

Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")      [visible after d0dc12e86b319]
Signed-off-by: Naoya Horiguchi <>
Co-developed-by: David Hildenbrand <>
Signed-off-by: David Hildenbrand <>
Reviewed-by: Yang Shi <>
Acked-by: Michal Hocko <>
Reviewed-by: Miaohe Lin <>
Reviewed-by: Oscar Salvador <>
Acked-by: Kirill A. Shutemov <>
Cc: Matthew Wilcox <>
Cc: Muchun Song <>
Cc: <>	[5.10+]
Signed-off-by: Andrew Morton <>
1 file changed