On Wed, Jan 19, 2011 at 11:21:50PM +0100, Andrea Arcangeli wrote:
> Hello Werner,
>
> this should fix your oops, it's untested still so let me know if you
> test it.
I tested this with ktest.pl on the config that was breaking for me. I
ran the test 20 times and it succeeded for all 20 tests.
Tested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
-- Steve
>
> It's a noop for x86_64 and it only affected x86 32bit with highpte enabled.
>
> ====
> Subject: khugepaged: fix pte_unmap for highpte x86_32
>
> From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>
> __collapse_huge_page_copy is still dereferencing the pte passed as parameter so
> we must pte_unmap after __collapse_huge_page_copy returns, not before.
>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 004c9c2..c4f634b 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1837,9 +1837,9 @@ static void collapse_huge_page(struct mm_struct *mm,
> spin_lock(ptl);
> isolated = __collapse_huge_page_isolate(vma, address, pte);
> spin_unlock(ptl);
> - pte_unmap(pte);
>
> if (unlikely(!isolated)) {
> + pte_unmap(pte);
> spin_lock(&mm->page_table_lock);
> BUG_ON(!pmd_none(*pmd));
> set_pmd_at(mm, address, pmd, _pmd);
> @@ -1856,6 +1856,7 @@ static void collapse_huge_page(struct mm_struct *mm,
> anon_vma_unlock(vma->anon_vma);
>
> __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
> + pte_unmap(pte);
> __SetPageUptodate(new_page);
> pgtable = pmd_pgtable(_pmd);
> VM_BUG_ON(page_count(pgtable) != 1);
>
>
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