On Tue, Aug 21, 2018 at 06:10:42PM -0700, Mike Kravetz wrote:
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3103099f64fd..f085019a4724 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4555,6 +4555,9 @@ static bool vma_shareable(struct vm_area_struct *vma,
> unsigned long addr)
>
> /*
> * check on proper vm_flags and page table alignment
> + *
> + * Note that this is the same check used in huge_pmd_sharing_possible.
> + * If you change one, consider changing both.
Should we have helper to isolate the check in one place?
> */
> if (vma->vm_flags & VM_MAYSHARE &&
> vma->vm_start <= base && end <= vma->vm_end)
> @@ -4562,6 +4565,43 @@ static bool vma_shareable(struct vm_area_struct *vma,
> unsigned long addr)
> return false;
> }
>
> +/*
> + * Determine if start,end range within vma could be mapped by shared pmd.
> + * If yes, adjust start and end to cover range associated with possible
> + * shared pmd mappings.
> + */
> +bool huge_pmd_sharing_possible(struct vm_area_struct *vma,
> + unsigned long *start, unsigned long *end)
> +{
> + unsigned long check_addr = *start;
> + bool ret = false;
> +
> + if (!(vma->vm_flags & VM_MAYSHARE))
> + return ret;
Do we ever use return value? I don't see it.
And in this case function name is not really work...
> + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
> + unsigned long a_start = check_addr & PUD_MASK;
> + unsigned long a_end = a_start + PUD_SIZE;
> +
> + /*
> + * If sharing is possible, adjust start/end if necessary.
> + *
> + * Note that this is the same check used in vma_shareable. If
> + * you change one, consider changing both.
> + */
> + if (vma->vm_start <= a_start && a_end <= vma->vm_end) {
> + if (a_start < *start)
> + *start = a_start;
> + if (a_end > *end)
> + *end = a_end;
> +
> + ret = true;
> + }
> + }
> +
> + return ret;
> +}
> +
--
Kirill A. Shutemov
