On 6 Feb 2017, at 0:12, Naoya Horiguchi wrote: > On Sun, Feb 05, 2017 at 11:12:39AM -0500, Zi Yan wrote: >> From: Zi Yan <ziy@xxxxxxxxxx> >> >> It allows splitting huge pmd while you are holding the pmd lock. >> It is prepared for future zap_pmd_range() use. >> >> Signed-off-by: Zi Yan <zi.yan@xxxxxxxxxxxxxx> >> --- >> include/linux/huge_mm.h | 2 ++ >> mm/huge_memory.c | 22 ++++++++++++---------- >> 2 files changed, 14 insertions(+), 10 deletions(-) >> > ... >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 03e4566fc226..cd66532ef667 100644 > ... >> @@ -2036,10 +2039,9 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, >> clear_page_mlock(page); >> } else if (!pmd_devmap(*pmd)) >> goto out; >> - __split_huge_pmd_locked(vma, pmd, haddr, freeze); >> + __split_huge_pmd_locked(vma, pmd, address, freeze); > > Could you explain what is intended on this change? > If some caller (f.e. wp_huge_pmd?) could call __split_huge_pmd() with > address not aligned with pmd border, __split_huge_pmd_locked() results in > triggering VM_BUG_ON(haddr & ~HPAGE_PMD_MASK). This change is intended for any caller already hold pmd lock. Now it is for this call site only. In Patch 2, I moved unsigned long haddr = address & HPAGE_PMD_MASK; from __split_huge_pmd() to __split_huge_pmd_locked(), so VM_BUG_ON(haddr & ~HPAGE_PMD_MASK) will not be triggered. > > Thanks, > Naoya Horiguchi > >> out: >> spin_unlock(ptl); >> - mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); >> } >> >> void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, >> -- >> 2.11.0 >> -- Best Regards Yan Zi
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