linux-kernel - Re: [PATCH 4/7] mm/hugetlb: Prepare hugetlb_follow_page_mask() for FOLL

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Message-ID: <533c32cf-9a18-1590-4d29-f076d6bd58c1@redhat.com>
Date:   Wed, 14 Jun 2023 16:57:37 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Rapoport <rppt@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        James Houghton <jthoughton@...gle.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 4/7] mm/hugetlb: Prepare hugetlb_follow_page_mask() for
 FOLL_PIN

On 13.06.23 23:53, Peter Xu wrote:
> It's coming, not yet, but soon.  Loose the restriction.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>   mm/hugetlb.c | 7 -------
>   1 file changed, 7 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index f037eaf9d819..31d8f18bc2e4 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6467,13 +6467,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>   	spinlock_t *ptl;
>   	pte_t *pte, entry;
>   
> -	/*
> -	 * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via
> -	 * follow_hugetlb_page().
> -	 */
> -	if (WARN_ON_ONCE(flags & FOLL_PIN))
> -		return NULL;
> -
>   	hugetlb_vma_lock_read(vma);
>   	pte = hugetlb_walk(vma, haddr, huge_page_size(h));
>   	if (!pte)
Did you fix why the warning was placed there in the first place? (IIRC, 
at least unsharing support needs to be added, maybe more)

-- 
Cheers,

David / dhildenb