linux-kernel - Re: [PATCH] documentation/mm: Update pmd_present() in arch_pgtable

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Date:   Wed, 23 Nov 2022 10:24:21 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc:     Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] documentation/mm: Update pmd_present() in
 arch_pgtable_helpers.rst

On 23.11.22 06:13, Anshuman Khandual wrote:
> Although pmd_present() might seem to indicate a valid and mapped pmd entry,
> in reality it returns true when pmd_page() points to a valid page in memory
> , regardless whether the pmd entry is mapped or not. Andrea Arcangeli had
> earlier explained [1] the required semantics for pmd_present(). This just
> updates the documentation for pmd_present() as required.
> 
> [1] https://lore.kernel.org/lkml/20181017020930.GN30832@redhat.com/
> 
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Mike Rapoport <rppt@...nel.org>
> Cc: linux-mm@...ck.org
> Cc: linux-doc@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This applies on v6.1-rc6
> 
> The latest trigger was from an earlier discussion here.
> 
> https://lore.kernel.org/all/53c0c955-7afe-905b-468a-cd7ac81238c5@arm.com/
> 
>   Documentation/mm/arch_pgtable_helpers.rst | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst
> index cbaee9e59241..fd2a19df884e 100644
> --- a/Documentation/mm/arch_pgtable_helpers.rst
> +++ b/Documentation/mm/arch_pgtable_helpers.rst
> @@ -94,7 +94,7 @@ PMD Page Table Helpers
>   +---------------------------+--------------------------------------------------+
>   | pmd_trans_huge            | Tests a Transparent Huge Page (THP) at PMD       |
>   +---------------------------+--------------------------------------------------+
> -| pmd_present               | Tests a valid mapped PMD                         |
> +| pmd_present               | Tests whether pmd_page() points to valid memory  |
>   +---------------------------+--------------------------------------------------+
>   | pmd_young                 | Tests a young PMD                                |
>   +---------------------------+--------------------------------------------------+

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

-- 
Thanks,

David / dhildenb