Commit d41e2f3b authored by Baoquan He's avatar Baoquan He Committed by Linus Torvalds
Browse files

mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

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
causes a 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:

Let's move the ->section_mem_map resetting after
depopulate_section_memmap() to fix it.

[ remove unneeded initialization, per David]
Fixes: ba72b4c8

 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by: default avatarBaoquan He <>
Signed-off-by: default avatarAndrew Morton <>
Reviewed-by: default avatarPankaj Gupta <>
Reviewed-by: default avatarDavid Hildenbrand <>
Acked-by: default avatarMichal Hocko <>
Cc: Wei Yang <>
Cc: Oscar Salvador <>
Cc: Mike Rapoport <>
Cc: <>

Signed-off-by: default avatarLinus Torvalds <>
parent 7d36665a
......@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
struct mem_section *ms = __pfn_to_section(pfn);
bool section_is_early = early_section(ms);
struct page *memmap = NULL;
bool empty;
unsigned long *subsection_map = ms->usage
? &ms->usage->subsection_map[0] : NULL;
......@@ -764,7 +765,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
* For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
if (empty) {
unsigned long section_nr = pfn_to_section_nr(pfn);
......@@ -779,13 +781,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
ms->usage = NULL;
memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
ms->section_mem_map = (unsigned long)NULL;
if (section_is_early && memmap)
depopulate_section_memmap(pfn, nr_pages, altmap);
if (empty)
ms->section_mem_map = (unsigned long)NULL;
static struct page * __meminit section_activate(int nid, unsigned long pfn,
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