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powerpc: disable assert_pte_locked for collapse_huge_page

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With THP we set pmd to none, before we do pte_clear. Hence we can't
walk page table to get the pte lock ptr and verify whether it is locked.
THP do take pte lock before calling pte_clear. So we don't change the locking
rules here. It is that we can't use page table walking to check whether
pte locks are held with THP.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Aneesh Kumar K.V 2013-06-20 14:30:24 +05:30 committed by Benjamin Herrenschmidt
parent 7888b4ddb4
commit a00e7bea0d
1 changed files with 8 additions and 0 deletions
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arch/powerpc/mm/pgtable.c
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@ -235,6 +235,14 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
pud = pud_offset(pgd, addr);
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, addr);
/*
* khugepaged to collapse normal pages to hugepage, first set
* pmd to none to force page fault/gup to take mmap_sem. After
* pmd is set to none, we do a pte_clear which does this assertion
* so if we find pmd none, return.
*/
if (pmd_none(*pmd))
return;
BUG_ON(!pmd_present(*pmd));
assert_spin_locked(pte_lockptr(mm, pmd));
}