On Mon, May 13, 2013 at 08:26:40PM +0530, Aneesh Kumar K.V wrote: > From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > > 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> > --- > 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; Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>