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    SubjectRe: [RFC PATCH 1/3] mm/thp: Use pmdp_splitting_flush_notify to clear pmd on splitting
    Date
    "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> writes:

    > "Kirill A. Shutemov" <kirill@shutemov.name> writes:
    >
    >>> @@ -184,3 +185,13 @@ void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
    >>> }
    >>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
    >>> #endif
    >>> +
    >>> +#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH_NOTIFY
    >>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    >>> +void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
    >>> + unsigned long address, pmd_t *pmdp)
    >>> +{
    >>> + pmdp_clear_flush_notify(vma, address, pmdp);
    >>> +}
    >>> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
    >>> +#endif
    >>
    >> I think it worth inlining. Let's put it to <asm-generic/pgtable.h>
    >>
    >> It probably worth combining with collapse counterpart in the same patch.
    >>
    >
    > I tried that first, But that pulls in mmu_notifier.h and huge_mm.h
    > headers and other build failures
    >

    Putting them in TRANSPATENT_HUGEPAGE helped.

    commit 9c60ab5d1d684db2ba454ee1c7f3e9a6bf57f026
    Author: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Date: Wed Apr 29 14:57:30 2015 +0530

    mm/thp: Use pmdp_splitting_flush_notify to clear pmd on splitting

    Some arch may require an explicit IPI before a THP PMD split. This
    ensures that a local_irq_disable can prevent a parallel THP PMD split.
    So use new function which arch can override

    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

    diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
    index fe617b7e4be6..6a0b2ab899d1 100644
    --- a/include/asm-generic/pgtable.h
    +++ b/include/asm-generic/pgtable.h
    @@ -184,6 +184,24 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
    #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
    #endif

    +#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH_NOTIFY
    +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    +static inline void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
    + unsigned long address,
    + pmd_t *pmdp)
    +{
    + pmdp_clear_flush_notify(vma, address, pmdp);
    +}
    +#else
    +static inline void pmdp_splitting_flush_notify(struct vm_area_struct *vma,
    + unsigned long address,
    + pmd_t *pmdp)
    +{
    + BUG();
    +}
    +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
    +#endif
    +
    #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
    extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
    pgtable_t pgtable);
    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index cce4604c192f..81e9578bf43a 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -2606,9 +2606,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,

    write = pmd_write(*pmd);
    young = pmd_young(*pmd);
    -
    - /* leave pmd empty until pte is filled */
    - pmdp_clear_flush_notify(vma, haddr, pmd);
    + /*
    + * leave pmd empty until pte is filled.
    + */
    + pmdp_splitting_flush_notify(vma, haddr, pmd);

    pgtable = pgtable_trans_huge_withdraw(mm, pmd);
    pmd_populate(mm, &_pmd, pgtable);


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