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/
Link: https://lkml.kernel.org/r/20221123051319.1312582-1-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst
index cbaee9e..fd2a19d 100644
--- a/Documentation/mm/arch_pgtable_helpers.rst
+++ b/Documentation/mm/arch_pgtable_helpers.rst
@@ -94,7 +94,7 @@
+---------------------------+--------------------------------------------------+
| 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 |
+---------------------------+--------------------------------------------------+
