linux-kernel - [PATCH v3 01/11] mm: Relocate the page table ceiling and floor definitions

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Message-ID: <20260121164946.2093480-2-Liam.Howlett@oracle.com>
Date: Wed, 21 Jan 2026 11:49:36 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Suren Baghdasaryan <surenb@...gle.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Pedro Falcato <pfalcato@...e.de>, David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Jann Horn <jannh@...gle.com>, shikemeng@...weicloud.com,
        kasong@...cent.com, nphamcs@...il.com, bhe@...hat.com,
        baohua@...nel.org, chrisl@...nel.org,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        SeongJae Park <sj@...nel.org>
Subject: [PATCH v3 01/11] mm: Relocate the page table ceiling and floor definitions

pgtables.h defines a fallback for ceiling and floor of the page tables
within the CONFIG_MMU section.  Moving the definitions to outside the
CONFIG_MMU Allows for using them in generic code.

Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Suggested-by: SeongJae Park <sj@...nel.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 include/linux/pgtable.h | 39 ++++++++++++++++++++-------------------
 mm/vma_internal.h       |  1 +
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index eb8aacba3698d..557ac918bdca6 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -22,25 +22,6 @@
 #error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{P4D,PUD,PMD}_FOLDED
 #endif
 
-/*
- * On almost all architectures and configurations, 0 can be used as the
- * upper ceiling to free_pgtables(): on many architectures it has the same
- * effect as using TASK_SIZE.  However, there is one configuration which
- * must impose a more careful limit, to avoid freeing kernel pgtables.
- */
-#ifndef USER_PGTABLES_CEILING
-#define USER_PGTABLES_CEILING	0UL
-#endif
-
-/*
- * This defines the first usable user address. Platforms
- * can override its value with custom FIRST_USER_ADDRESS
- * defined in their respective <asm/pgtable.h>.
- */
-#ifndef FIRST_USER_ADDRESS
-#define FIRST_USER_ADDRESS	0UL
-#endif
-
 /*
  * This defines the generic helper for accessing PMD page
  * table page. Although platforms can still override this
@@ -1660,6 +1641,26 @@ void arch_sync_kernel_mappings(unsigned long start, unsigned long end);
 
 #endif /* CONFIG_MMU */
 
+/*
+ * On almost all architectures and configurations, 0 can be used as the
+ * upper ceiling to free_pgtables(): on many architectures it has the same
+ * effect as using TASK_SIZE.  However, there is one configuration which
+ * must impose a more careful limit, to avoid freeing kernel pgtables.
+ */
+#ifndef USER_PGTABLES_CEILING
+#define USER_PGTABLES_CEILING	0UL
+#endif
+
+/*
+ * This defines the first usable user address. Platforms
+ * can override its value with custom FIRST_USER_ADDRESS
+ * defined in their respective <asm/pgtable.h>.
+ */
+#ifndef FIRST_USER_ADDRESS
+#define FIRST_USER_ADDRESS	0UL
+#endif
+
+
 /*
  * No-op macros that just return the current protection value. Defined here
  * because these macros can be used even if CONFIG_MMU is not defined.
diff --git a/mm/vma_internal.h b/mm/vma_internal.h
index 2f05735ff190c..2da6d224c1a85 100644
--- a/mm/vma_internal.h
+++ b/mm/vma_internal.h
@@ -46,6 +46,7 @@
 #include <linux/swap.h>
 #include <linux/uprobes.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/pgtable.h>
 
 #include <asm/current.h>
 #include <asm/tlb.h>
-- 
2.47.3