The patch titled
Subject: mm/THP: use pmd_populate() to update the pmd with pgtable_t pointer
has been added to the -mm tree. Its filename is
mm-thp-use-pmd_populate-to-update-the-pmd-with-pgtable_t-pointer.patch
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From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Subject: mm/THP: use pmd_populate() to update the pmd with pgtable_t pointer
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.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN mm/huge_memory.c~mm-thp-use-pmd_populate-to-update-the-pmd-with-pgtable_t-pointer mm/huge_memory.c
--- a/mm/huge_memory.c~mm-thp-use-pmd_populate-to-update-the-pmd-with-pgtable_t-pointer
+++ a/mm/huge_memory.c
@@ -2325,7 +2325,12 @@ static void collapse_huge_page(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;
_
Patches currently in -mm which might be from aneesh.kumar@xxxxxxxxxxxxxxxxxx are
mm-thp-use-pmd_populate-to-update-the-pmd-with-pgtable_t-pointer.patch
mm-thp-use-the-right-function-when-updating-access-flags.patch
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