Re: [PATCH v2 35/46] hugetlb: add check to prevent refcount overflow via HGM

[James Houghton <jthoughton@xxxxxxxxxx>]

> @@ -5397,7 +5397,10 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>                 } else {
>                         ptepage = pte_page(entry);
>                         hpage = compound_head(ptepage);
> -                       get_page(hpage);
> +                       if (try_get_page(hpage)) {
> +                               ret = -EFAULT;
> +                               break;

spin_unlock(src_ptl) and spin_unlock(dst_ptl) is required here.

I'll make sure there's a selftest that actually makes sure that
refcount overflowing is handled gracefully for v3.

> +                       }
>
>                         /*
>                          * Failing to duplicate the anon rmap is a rare case
> @@ -6132,6 +6135,30 @@ static bool hugetlb_pte_stable(struct hstate *h, struct hugetlb_pte *hpte,
>         return same;
>  }