Message-ID: <69e08e1c-88f6-bf93-523a-b65ffb9235c5@redhat.com>
Date:   Fri, 3 Mar 2023 10:10:37 +0100
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Subject: Re: [PATCH] mm: teach mincore_hugetlb about pte markers
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To:     James Houghton <jthoughton@google.com>,
        Peter Xu <peterx@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Axel Rasmussen <axelrasmussen@google.com>,
        Anish Moorthy <amoorthy@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20230302222404.175303-1-jthoughton@google.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230302222404.175303-1-jthoughton@google.com>
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On 02.03.23 23:24, James Houghton wrote:
> By checking huge_pte_none(), we incorrectly classify PTE markers as
> "present". Instead, check huge_pte_none_mostly(), classifying PTE
> markers the same as if the PTE were completely blank.
> 
> PTE markers, unlike other kinds of swap entries, don't reference any
> physical page and don't indicate that a physical page was mapped
> previously. As such, treat them as non-present for the sake of
> mincore().
> 
> Fixes: 5c041f5d1f23 ("mm: teach core mm about pte markers")
> Signed-off-by: James Houghton <jthoughton@google.com>
> ---
>   mm/mincore.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mincore.c b/mm/mincore.c
> index cd69b9db0081..d359650b0f75 100644
> --- a/mm/mincore.c
> +++ b/mm/mincore.c
> @@ -33,7 +33,7 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
>   	 * Hugepages under user process are always in RAM and never
>   	 * swapped out, but theoretically it needs to be checked.
>   	 */
> -	present = pte && !huge_pte_none(huge_ptep_get(pte));
> +	present = pte && !huge_pte_none_mostly(huge_ptep_get(pte));
>   	for (; addr != end; vec++, addr += PAGE_SIZE)
>   		*vec = present;
>   	walk->private = vec;

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb