linux-kernel - Re: [PATCH 19/46] hugetlb: add HGM support for follow_hugetlb

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Message-ID: <Y7dOghlx5CDQtHyF@x1n>
Date:   Thu, 5 Jan 2023 17:26:10 -0500
From:   Peter Xu <peterx@...hat.com>
To:     James Houghton <jthoughton@...gle.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 19/46] hugetlb: add HGM support for follow_hugetlb_page

On Thu, Jan 05, 2023 at 10:18:17AM +0000, James Houghton wrote:
> @@ -6649,13 +6655,20 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  		 */
>  		if (absent && (flags & FOLL_DUMP) &&
>  		    !hugetlbfs_pagecache_present(h, vma, vaddr)) {
> -			if (pte)
> +			if (ptep)
>  				spin_unlock(ptl);
>  			hugetlb_vma_unlock_read(vma);
>  			remainder = 0;
>  			break;
>  		}
>  
> +		if (!absent && pte_present(pte) &&
> +				!hugetlb_pte_present_leaf(&hpte, pte)) {
> +			/* We raced with someone splitting the PTE, so retry. */
> +			spin_unlock(ptl);

vma unlock missing here.

> +			continue;
> +		}

-- 
Peter Xu