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

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Date:   Wed, 23 Nov 2022 10:43:19 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        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: [PATCH] documentation/mm: Update pmd_present() in arch_pgtable_helpers.rst

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                                |
 +---------------------------+--------------------------------------------------+
-- 
2.25.1