On Thu 16-06-16 19:36:11, zhongjiang wrote:
> From: zhong jiang <zhongjiang@xxxxxxxxxx>
>
> when a process acquire a pmd table shared by other process, we
> increase the account to current process. otherwise, a race result
> in other tasks have set the pud entry. so it no need to increase it.
>
> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 19d0d08..3b025c5 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4189,10 +4189,9 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
> if (pud_none(*pud)) {
> pud_populate(mm, pud,
> (pmd_t *)((unsigned long)spte & PAGE_MASK));
> - } else {
> + } else
> put_page(virt_to_page(spte));
> - mm_inc_nr_pmds(mm);
> - }
The code is quite puzzling but is this correct? Shouldn't we rather do
mm_dec_nr_pmds(mm) in that path to undo the previous inc?
> +
> spin_unlock(ptl);
> out:
> pte = (pte_t *)pmd_alloc(mm, pud, addr);
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
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