linux-kernel - Re: [PATCH v2 2/3] mm/hugetlb: Use hugetlb_pte

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Date:   Mon, 3 Oct 2022 19:35:05 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2/3] mm/hugetlb: Use hugetlb_pte_stable in migration
 race check

On 10/03/22 20:37, Peter Xu wrote:
> After hugetlb_pte_stable() introduced, we can also rewrite the migration
> race condition against page allocation to use the new helper too.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  mm/hugetlb.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz

> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index fa3fcdb0c4b8..e762c5369a6f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5620,11 +5620,10 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
>  			 * here.  Before returning error, get ptl and make
>  			 * sure there really is no pte entry.
>  			 */
> -			ptl = huge_pte_lock(h, mm, ptep);
> -			ret = 0;
> -			if (huge_pte_none(huge_ptep_get(ptep)))
> +			if (hugetlb_pte_stable(h, mm, ptep, old_pte))
>  				ret = vmf_error(PTR_ERR(page));
> -			spin_unlock(ptl);
> +			else
> +				ret = 0;
>  			goto out;
>  		}
>  		clear_huge_page(page, address, pages_per_huge_page(h));
> -- 
> 2.37.3
>