From: Pavel Tatashin pasha.tatashin@oracle.com Subject: mm: sections are not offlined during memory hotremove

Memory hotplug and hotremove operate with per-block granularity. If the machine has a large amount of memory (more than 64G), the size of a memory block can span multiple sections. By mistake, during hotremove we set only the first section to offline state.

The bug was discovered because kernel selftest started to fail: https://lkml.kernel.org/r/20180423011247.GK5563@yexl-desktop

After commit, "mm/memory_hotplug: optimize probe routine". But, the bug is older than this commit. In this optimization we also added a check for sections to be in a proper state during hotplug operation.

Link: http://lkml.kernel.org/r/20180427145257.15222-1-pasha.tatashin@oracle.com Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes") Signed-off-by: Pavel Tatashin pasha.tatashin@oracle.com Acked-by: Michal Hocko mhocko@suse.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Steven Sistare steven.sistare@oracle.com Cc: Daniel Jordan daniel.m.jordan@oracle.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/sparse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN mm/sparse.c~mm-sections-are-not-offlined-during-memory-hotremove mm/sparse.c --- a/mm/sparse.c~mm-sections-are-not-offlined-during-memory-hotremove +++ a/mm/sparse.c @@ -629,7 +629,7 @@ void offline_mem_sections(unsigned long unsigned long pfn;

for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { - unsigned long section_nr = pfn_to_section_nr(start_pfn); + unsigned long section_nr = pfn_to_section_nr(pfn); struct mem_section *ms;

/* _