Re: [PATCH v2 08/10] mm/vma: Use unmap_desc in exit_mmap() and vms_clear_ptes()

[SeongJae Park <sj@kernel.org>]

On Fri, 16 Jan 2026 11:15:43 -0500 "Liam R. Howlett" <Liam.Howlett@oracle.com> wrote:

> * Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [260116 03:27]:
> > On Fri, Jan 16, 2026 at 10:04:27AM +0800, kernel test robot wrote:
> > > Hi Liam,
> > >
> > > kernel test robot noticed the following build errors:
> > >
> > > [auto build test ERROR on akpm-mm/mm-everything]
> > > [also build test ERROR on linus/master v6.19-rc5 next-20260115]
> > > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > > And when submitting patch, we suggest to use '--base' as documented in
> > > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > >
> > > url:    https://github.com/intel-lab-lkp/linux/commits/Liam-R-Howlett/mm-mmap-Move-exit_mmap-trace-point/20260116-023126
> > > base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> > > patch link:    https://lore.kernel.org/r/20260115182720.1691130-9-Liam.Howlett%40oracle.com
> > > patch subject: [PATCH v2 08/10] mm/vma: Use unmap_desc in exit_mmap() and vms_clear_ptes()
> > > config: m68k-allnoconfig (https://download.01.org/0day-ci/archive/20260116/202601160925.VR8a2hUw-lkp@intel.com/config)
> > > compiler: m68k-linux-gcc (GCC) 15.2.0
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260116/202601160925.VR8a2hUw-lkp@intel.com/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202601160925.VR8a2hUw-lkp@intel.com/
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > >    In file included from mm/internal.h:23,
> > >                     from mm/filemap.c:54:
> > >    mm/vma.h: In function 'unmap_all_init':
> > > >> mm/vma.h:175:27: error: 'FIRST_USER_ADDRESS' undeclared (first use in this function)
> > >      175 |         unmap->pg_start = FIRST_USER_ADDRESS;
> > >          |                           ^~~~~~~~~~~~~~~~~~
> > >    mm/vma.h:175:27: note: each undeclared identifier is reported only once for each function it appears in
> > > >> mm/vma.h:176:25: error: 'USER_PGTABLES_CEILING' undeclared (first use in this function)
> > >      176 |         unmap->pg_end = USER_PGTABLES_CEILING;
> > >          |                         ^~~~~~~~~~~~~~~~~~~~~
> > >
> > 
> > Suspect you need to add:
> > 
> > #include <linux/pgtable.h>
> > 
> > to mm/vma_internal.h.
> > 
> > Some arches don't define it and that header has:
> > 
> > #ifndef USER_PGTABLES_CEILING
> > #define USER_PGTABLES_CEILING	0UL
> > #endif
> > 
> > ...
> > 
> > #ifndef FIRST_USER_ADDRESS
> > #define FIRST_USER_ADDRESS	0UL
> > #endif

But the macro definitions are enclosed by '#ifdef CONFIG_MMU'.  I have
!CONFIG_MMU build test, which shows similar errors, even after Lorenzo's
suggestion is applied.  Should we move the definitions out of the '#ifdef
CONFIG_MMU', or implement another unmap_all_init() for !CONFIG_MMU case?

I confirmed a simple version of the first option (moving definitions out of
CONFIG_MMU, in addition to including pgtable.h) like below works at least for
my !CONFIG_MMU test.


Thanks,
SJ

[...]
=== >8 ===
From d5b441af2f31164a46240ce4179db8e0d2fff372 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@kernel.org>
Date: Fri, 16 Jan 2026 17:01:27 -0800
Subject: [PATCH] mm/vma: temporal build fix

Link: https://lkml.kernel.org/r/20260115182720.1691130-9-Liam.Howlett@oracle.com
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/pgtable.h | 38 +++++++++++++++++++-------------------
 mm/vma_internal.h       |  1 +
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index ce2dbebade4c..4f063438a4fc 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 +1641,25 @@ 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 2f05735ff190..2da6d224c1a8 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