From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
We should not use set_pmd_at to update pmd_t with pgtable_t pointer. set_pmd_at
is used to set pmd with huge pte entries and architectures like ppc64, clear
few flags from the pte when saving a new entry. Without this change we observe
bad pte errors like below on ppc64 with THP enabled.
BUG: Bad page map in process ld mm=0xc000001ee39f4780 pte:7fc3f37848000001
pmd:c000001ec0000000
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
mm/huge_memory.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 03a89a2..362c329 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2325,7 +2325,12 @@ static void collapse_huge_page(struct mm_struct *mm,
pte_unmap(pte);
spin_lock(&mm->page_table_lock);
BUG_ON(!pmd_none(*pmd));
- set_pmd_at(mm, address, pmd, _pmd);
+ /*
+ * We can only use set_pmd_at when establishing
+ * hugepmds and never for establishing regular pmds that
+ * points to regular pagetables. Use pmd_populate for that
+ */
+ pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(&mm->page_table_lock);
anon_vma_unlock_write(vma->anon_vma);
goto out;
--
1.8.1.2
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