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    SubjectRe: [PATCH v4 15/20] powerpc/mm: Avoid useless lock with single page fragments
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    On 9/18/18 10:27 PM, Christophe Leroy wrote:
    > There is no point in taking the page table lock as
    > pte_frag is always NULL when we have only one fragment.
    >
    > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
    > ---
    > arch/powerpc/mm/pgtable-frag.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
    > index bc924822dcd6..ab4910e92aaf 100644
    > --- a/arch/powerpc/mm/pgtable-frag.c
    > +++ b/arch/powerpc/mm/pgtable-frag.c
    > @@ -85,6 +85,9 @@ static pte_t *get_pte_from_cache(struct mm_struct *mm)
    > {
    > void *pte_frag, *ret;
    >
    > + if (PTE_FRAG_NR == 1)
    > + return NULL;
    > +
    > spin_lock(&mm->page_table_lock);
    > ret = mm->context.pte_frag;
    > if (ret) {
    >

    May be update get_pmd_from_cache too?

    -aneesh

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