On Thu, 2 Oct 2014, Mel Gorman wrote:
> PROT_NUMA VMAs are skipped to avoid problems distinguishing between
> present, prot_none and special entries. MPOL_MF_LAZY is not visible from
> userspace since commit a720094ded8c ("mm: mempolicy: Hide MPOL_NOOP and
> MPOL_MF_LAZY from userspace for now") but it should still skip VMAs the
> same way task_numa_work does.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Yes, this is much the same as the patch I wrote for Linus two days ago,
then discovered that we don't need until MPOL_MF_LAZY gets brought back
into MPOL_MF_VALID. (As a bonus, my patch did also remove the currently
bogus paragraph of comment above change_prot_numa(); and I would prefer a
code comment to make clear that we never exercise this path at present.)
> ---
> mm/mempolicy.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 8f5330d..a5877ce 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -683,7 +683,9 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
> }
>
> if (flags & MPOL_MF_LAZY) {
> - change_prot_numa(vma, start, endvma);
> + /* Similar to task_numa_work, skip inaccessible VMAs */
> + if (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
> + change_prot_numa(vma, start, endvma);
> goto next;
> }
>
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