[PATCH] documentation/mm: Update pmd_present() in arch_pgtable_helpers.rst

[PATCH] documentation/mm: Update pmd_present() in arch_pgtable_helpers.rst

[Anshuman Khandual]

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@lwn.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: linux-mm@kvack.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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                                |
 +---------------------------+--------------------------------------------------+
-- 
2.25.1

Re: [PATCH] documentation/mm: Update pmd_present() in arch_pgtable_helpers.rst

[David Hildenbrand]

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@lwn.net>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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@redhat.com>

-- 
Thanks,

David / dhildenb