Re: [PATCH v5 03/11] thp: copy_huge_pmd(): copy huge zero page

David Rientjes
2012-11-14T22:33:49Z

On Wed, 7 Nov 2012, Kirill A. Shutemov wrote:

> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index ff834ea..0d903bf 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -701,6 +701,18 @@ static inline struct page *alloc_hugepage(int defrag)
> }
> #endif
>
> +static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
> + struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd)
> +{
> + pmd_t entry;
> + entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot);
> + entry = pmd_wrprotect(entry);
> + entry = pmd_mkhuge(entry);
> + set_pmd_at(mm, haddr, pmd, entry);
> + pgtable_trans_huge_deposit(mm, pgtable);
> + mm->nr_ptes++;
> +}
> +
> int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
> unsigned long address, pmd_t *pmd,
> unsigned int flags)
> @@ -778,6 +790,11 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> pte_free(dst_mm, pgtable);
> goto out_unlock;
> }
> + if (is_huge_zero_pmd(pmd)) {
> + set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd);
> + ret = 0;
> + goto out_unlock;
> + }

You said in the introduction message in this series that you still allow
splitting of the pmd, so why no check for pmd_trans_splitting() before
this?