[PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[Hui Zhu]

From: Hui Zhu <zhuhui@kylinos.cn>

KCSAN reports a data race between page_to_nid()/folio_pgdat() reading
page->flags and folio_trylock()/folio_lock() concurrently doing
test_and_set_bit_lock(PG_locked, ...) on the same word, e.g.:

  BUG: KCSAN: data-race in __lruvec_stat_mod_folio / shmem_get_folio_gfp

The node id and zone id occupy fixed bit-ranges of page->flags that
are set once at page init and never modified afterwards, so they can
never overlap with the low PG_locked/PG_waiters bits touched by the
folio lock path.

ASSERT_EXCLUSIVE_BITS(mdf.f, ...) inside memdesc_nid()/memdesc_zonenum()
used to check a by-value copy of the flags word, not the actual shared
page->flags/folio->flags being modified concurrently, so it didn't
reliably assert anything about the real race.

For zonenum, move the assertion out of memdesc_zonenum() into
page_zonenum() and folio_zonenum(), where flags is dereferenced
directly from the page/folio.

For nid, turn memdesc_nid() into a macro instead, so the mdf argument
is expanded as the caller's own flags expression
(PF_POISONED_CHECK(page)->flags or folio->flags) rather than copied
into a function parameter, letting ASSERT_EXCLUSIVE_BITS() check the
real page->flags/folio->flags directly.

On CONFIG_NUMA=n, NODES_MASK is 0 and the old memdesc_nid() body
folded to a constant, so page->flags/folio->flags was never actually
read. ASSERT_EXCLUSIVE_BITS() is a real runtime check that can't be
folded away, so doing it unconditionally would add a pointless read
of page->flags/folio->flags and a check that can never fire. Keep
page_to_nid()/folio_nid() as plain "return 0" static inline stubs
under CONFIG_NUMA=n instead.

Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
---
Changelog:
v7:
According to the comments of Sashiko, restrict the memdesc_nid() macro
to CONFIG_NUMA, keeping a plain "return 0" static inline stub otherwise,
and re-add a local page pointer in page_to_nid() to avoid evaluating
PF_POISONED_CHECK(page) twice.
v6:
According to the comments of David, turn memdesc_nid() from a static
inline function into a macro so ASSERT_EXCLUSIVE_BITS() can check the
caller's page->flags/folio->flags directly.
v5:
According to the comments of Sashiko, guard the ASSERT_EXCLUSIVE_BITS()
calls with #ifndef NODE_NOT_IN_PAGE_FLAGS (for nid) and #if
ZONES_WIDTH != 0 (for zonenum).
According to the comments of David, avoid calling
PF_POISONED_CHECK(page) twice in page_to_nid().
According to the warning of lkp, switch the CONFIG_NUMA=n
page_to_nid()/folio_nid() stubs from macros to static inline functions.
v4:
According to the comments of Andrew and Sashiko, set
page_to_nid()/folio_nid() as static inline stubs returning 0
under CONFIG_NUMA=n.
v3:
According to the comments of Andrew and Sashiko, move
ASSERT_EXCLUSIVE_BITS out of memdesc_nid()/memdesc_zonenum()
into the page/folio call sites.
v2:
According to the comments of David, remove useless comments and use
ASSERT_EXCLUSIVE_BITS() in memdesc_nid() instead of data_race() in
page_to_nid().

 include/linux/mm.h     | 25 +++++++++++++++++++++++--
 include/linux/mmzone.h |  7 ++++++-
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 485df9c2dbdd..63fcf277b675 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2288,21 +2288,42 @@ static inline int page_zone_id(struct page *page)
 #ifdef NODE_NOT_IN_PAGE_FLAGS
 int memdesc_nid(memdesc_flags_t mdf);
 #else
+#ifdef CONFIG_NUMA
+#define memdesc_nid(mdf)						\
+({									\
+	ASSERT_EXCLUSIVE_BITS(mdf.f, NODES_MASK << NODES_PGSHIFT);	\
+	(int)((mdf.f >> NODES_PGSHIFT) & NODES_MASK);			\
+})
+#else
 static inline int memdesc_nid(memdesc_flags_t mdf)
 {
-	return (mdf.f >> NODES_PGSHIFT) & NODES_MASK;
+	return 0;
 }
 #endif
 
+#ifdef CONFIG_NUMA
 static inline int page_to_nid(const struct page *page)
 {
-	return memdesc_nid(PF_POISONED_CHECK(page)->flags);
+	const struct page *p = PF_POISONED_CHECK(page);
+
+	return memdesc_nid(p->flags);
 }
 
 static inline int folio_nid(const struct folio *folio)
 {
 	return memdesc_nid(folio->flags);
 }
+#else
+static inline int page_to_nid(const struct page *page)
+{
+	return 0;
+}
+
+static inline int folio_nid(const struct folio *folio)
+{
+	return 0;
+}
+#endif
 
 #ifdef CONFIG_NUMA_BALANCING
 /* page access time bits needs to hold at least 4 seconds */
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ca2712187147..1b4336098113 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1274,17 +1274,22 @@ static inline bool zone_is_empty(const struct zone *zone)
 
 static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags)
 {
-	ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT);
 	return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK;
 }
 
 static inline enum zone_type page_zonenum(const struct page *page)
 {
+#if ZONES_WIDTH != 0
+	ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT);
+#endif
 	return memdesc_zonenum(page->flags);
 }
 
 static inline enum zone_type folio_zonenum(const struct folio *folio)
 {
+#if ZONES_WIDTH != 0
+	ASSERT_EXCLUSIVE_BITS(folio->flags, ZONES_MASK << ZONES_PGSHIFT);
+#endif
 	return memdesc_zonenum(folio->flags);
 }
 
-- 
2.43.0

Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[kernel test robot]

Hi Hui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Hui-Zhu/mm-assert-exclusive-nid-zonenum-bits-at-the-page-folio-access-sites/20260626-112119
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260626032012.1049667-1-hui.zhu%40linux.dev
patch subject: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20260626/202606261253.X4CwKZZJ-lkp@intel.com/config)
compiler: clang version 22.1.3 (https://github.com/llvm/llvm-project e9846648fd6183ee6d8cbdb4502213fcf902a211)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260626/202606261253.X4CwKZZJ-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/202606261253.X4CwKZZJ-lkp@intel.com/

All errors (new ones prefixed by >>):

   WARN /zdci/src/lkp/lib/log.sh:131:in `log_warn': /opt/cross/rustc-1.96.0-bindgen-0.72.1 doesn't exist
     from /zdci/src/kernel-tests/lib/debug.sh:164: kbuild_log_warn
     from /zdci/src/kernel-tests/lib/kbuild.sh:3371: export_rust_path
     from /zdci/src/kernel-tests/lib/kbuild.sh:3361: export_compiler_path
     from /zdci/src/kernel-tests/lib/kbuild.sh:3840: invoke_make
     from /zdci/src/kernel-tests/lib/kbuild.sh:4022: make
     from /zdci/src/kernel-tests/common.sh:202: redirect_error_to_screen
     from /zdci/src/kernel-tests/common.sh:210: redirect_command_errors
     from /zdci/src/kernel-tests/lib/kbuild.sh:5680: make_prepare
     from /zdci/src/kernel-tests/lib/kbuild.sh:5909: test_kernel_build
     from /zdci/src/kernel-tests/lib/builder/base.sh:442: builder_execute_build
     from /zdci/src/kernel-tests/lib/kbuild.sh:6419: compile_one_config
     from /zdci/src/kernel-tests/lib/builder/base.sh:88: builder_compile
     from /zdci/src/kernel-tests/bisect-test-build-error.sh:102: main
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:21:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:23:
   In file included from include/linux/writeback.h:13:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:8:
   In file included from include/linux/cacheflush.h:5:
   In file included from arch/x86/include/asm/cacheflush.h:5:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:23:
   In file included from include/linux/writeback.h:13:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:10:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:13:
   In file included from include/linux/pagemap.h:8:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:13:
   In file included from include/linux/pagemap.h:17:
   In file included from include/linux/hugetlb_inline.h:5:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:9:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   6 errors generated.
   make[3]: *** [scripts/Makefile.build:184: arch/x86/kernel/asm-offsets.s] Error 1
   make[3]: Target 'prepare' not remade because of errors.
   make[2]: *** [Makefile:1390: prepare0] Error 2
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'prepare' not remade because of errors.


vim +2 include/linux/mm.h

^1da177e4c3f41 Linus Torvalds 2005-04-16 @2  #ifndef _LINUX_MM_H
^1da177e4c3f41 Linus Torvalds 2005-04-16  3  #define _LINUX_MM_H
^1da177e4c3f41 Linus Torvalds 2005-04-16  4  

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[kernel test robot]

Hi Hui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Hui-Zhu/mm-assert-exclusive-nid-zonenum-bits-at-the-page-folio-access-sites/20260626-112119
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260626032012.1049667-1-hui.zhu%40linux.dev
patch subject: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites
config: nios2-allnoconfig (https://download.01.org/0day-ci/archive/20260626/202606261257.rnknH3QK-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260626/202606261257.rnknH3QK-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/202606261257.rnknH3QK-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/linux/pid_namespace.h:7,
                    from include/linux/ptrace.h:10,
                    from arch/nios2/kernel/asm-offsets.c:10:
>> include/linux/mm.h:2: error: unterminated #ifndef
       2 | #ifndef _LINUX_MM_H
         | 
   make[3]: *** [scripts/Makefile.build:184: arch/nios2/kernel/asm-offsets.s] Error 1
   make[3]: Target 'prepare' not remade because of errors.
   make[2]: *** [Makefile:1390: prepare0] Error 2
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'prepare' not remade because of errors.


vim +2 include/linux/mm.h

^1da177e4c3f41 Linus Torvalds 2005-04-16 @2  #ifndef _LINUX_MM_H
^1da177e4c3f41 Linus Torvalds 2005-04-16  3  #define _LINUX_MM_H
^1da177e4c3f41 Linus Torvalds 2005-04-16  4  

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[Leon Hwang]

On 26/6/26 11:20, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
> 
> KCSAN reports a data race between page_to_nid()/folio_pgdat() reading
> page->flags and folio_trylock()/folio_lock() concurrently doing
> test_and_set_bit_lock(PG_locked, ...) on the same word, e.g.:
> 
>   BUG: KCSAN: data-race in __lruvec_stat_mod_folio / shmem_get_folio_gfp
> 
> The node id and zone id occupy fixed bit-ranges of page->flags that
> are set once at page init and never modified afterwards, so they can
> never overlap with the low PG_locked/PG_waiters bits touched by the
> folio lock path.
> 
> ASSERT_EXCLUSIVE_BITS(mdf.f, ...) inside memdesc_nid()/memdesc_zonenum()
> used to check a by-value copy of the flags word, not the actual shared
> page->flags/folio->flags being modified concurrently, so it didn't
> reliably assert anything about the real race.
> 
> For zonenum, move the assertion out of memdesc_zonenum() into
> page_zonenum() and folio_zonenum(), where flags is dereferenced
> directly from the page/folio.
> 
> For nid, turn memdesc_nid() into a macro instead, so the mdf argument
> is expanded as the caller's own flags expression
> (PF_POISONED_CHECK(page)->flags or folio->flags) rather than copied
> into a function parameter, letting ASSERT_EXCLUSIVE_BITS() check the
> real page->flags/folio->flags directly.
> 
> On CONFIG_NUMA=n, NODES_MASK is 0 and the old memdesc_nid() body
> folded to a constant, so page->flags/folio->flags was never actually
> read. ASSERT_EXCLUSIVE_BITS() is a real runtime check that can't be
> folded away, so doing it unconditionally would add a pointless read
> of page->flags/folio->flags and a check that can never fire. Keep
> page_to_nid()/folio_nid() as plain "return 0" static inline stubs
> under CONFIG_NUMA=n instead.
> 
> Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
> ---
> Changelog:
> v7:
> According to the comments of Sashiko, restrict the memdesc_nid() macro
> to CONFIG_NUMA, keeping a plain "return 0" static inline stub otherwise,
> and re-add a local page pointer in page_to_nid() to avoid evaluating
> PF_POISONED_CHECK(page) twice.
> v6:
> According to the comments of David, turn memdesc_nid() from a static
> inline function into a macro so ASSERT_EXCLUSIVE_BITS() can check the
> caller's page->flags/folio->flags directly.
> v5:
> According to the comments of Sashiko, guard the ASSERT_EXCLUSIVE_BITS()
> calls with #ifndef NODE_NOT_IN_PAGE_FLAGS (for nid) and #if
> ZONES_WIDTH != 0 (for zonenum).
> According to the comments of David, avoid calling
> PF_POISONED_CHECK(page) twice in page_to_nid().
> According to the warning of lkp, switch the CONFIG_NUMA=n
> page_to_nid()/folio_nid() stubs from macros to static inline functions.
> v4:
> According to the comments of Andrew and Sashiko, set
> page_to_nid()/folio_nid() as static inline stubs returning 0
> under CONFIG_NUMA=n.
> v3:
> According to the comments of Andrew and Sashiko, move
> ASSERT_EXCLUSIVE_BITS out of memdesc_nid()/memdesc_zonenum()
> into the page/folio call sites.
> v2:
> According to the comments of David, remove useless comments and use
> ASSERT_EXCLUSIVE_BITS() in memdesc_nid() instead of data_race() in
> page_to_nid().
> 
>  include/linux/mm.h     | 25 +++++++++++++++++++++++--
>  include/linux/mmzone.h |  7 ++++++-
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 485df9c2dbdd..63fcf277b675 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2288,21 +2288,42 @@ static inline int page_zone_id(struct page *page)
>  #ifdef NODE_NOT_IN_PAGE_FLAGS
>  int memdesc_nid(memdesc_flags_t mdf);
>  #else
> +#ifdef CONFIG_NUMA
> +#define memdesc_nid(mdf)						\
> +({									\
> +	ASSERT_EXCLUSIVE_BITS(mdf.f, NODES_MASK << NODES_PGSHIFT);	\
> +	(int)((mdf.f >> NODES_PGSHIFT) & NODES_MASK);			\
> +})
> +#else
>  static inline int memdesc_nid(memdesc_flags_t mdf)
>  {
> -	return (mdf.f >> NODES_PGSHIFT) & NODES_MASK;
> +	return 0;
>  }
>  #endif
>  
> +#ifdef CONFIG_NUMA
>  static inline int page_to_nid(const struct page *page)
>  {
> -	return memdesc_nid(PF_POISONED_CHECK(page)->flags);
> +	const struct page *p = PF_POISONED_CHECK(page);
> +
> +	return memdesc_nid(p->flags);
>  }
>  
>  static inline int folio_nid(const struct folio *folio)
>  {
>  	return memdesc_nid(folio->flags);
>  }
> +#else
> +static inline int page_to_nid(const struct page *page)
> +{
> +	return 0;
> +}
> +
> +static inline int folio_nid(const struct folio *folio)
> +{
> +	return 0;
> +}
> +#endif
>  
>  #ifdef CONFIG_NUMA_BALANCING
>  /* page access time bits needs to hold at least 4 seconds */
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index ca2712187147..1b4336098113 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1274,17 +1274,22 @@ static inline bool zone_is_empty(const struct zone *zone)
>  
>  static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags)
>  {
> -	ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT);
>  	return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK;
>  }
>  
>  static inline enum zone_type page_zonenum(const struct page *page)
>  {
> +#if ZONES_WIDTH != 0
> +	ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT);
> +#endif
>  	return memdesc_zonenum(page->flags);
>  }
>  
>  static inline enum zone_type folio_zonenum(const struct folio *folio)
>  {
> +#if ZONES_WIDTH != 0
> +	ASSERT_EXCLUSIVE_BITS(folio->flags, ZONES_MASK << ZONES_PGSHIFT);
> +#endif
>  	return memdesc_zonenum(folio->flags);
>  }
>  

Better to factor out a common macro alongside a comment for these two '#if'?

Thanks,
Leon

Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[kernel test robot]

Hi Hui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Hui-Zhu/mm-assert-exclusive-nid-zonenum-bits-at-the-page-folio-access-sites/20260626-112119
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260626032012.1049667-1-hui.zhu%40linux.dev
patch subject: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20260626/202606260757.WdVU9G1N-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260626/202606260757.WdVU9G1N-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/202606260757.WdVU9G1N-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:21:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:23:
   In file included from include/linux/writeback.h:13:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:8:
   In file included from include/linux/cacheflush.h:5:
   In file included from arch/x86/include/asm/cacheflush.h:5:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:23:
   In file included from include/linux/writeback.h:13:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:10:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:13:
   In file included from include/linux/pagemap.h:8:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:13:
   In file included from include/linux/pagemap.h:17:
   In file included from include/linux/hugetlb_inline.h:5:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:9:
>> include/linux/mm.h:2:2: error: unterminated conditional directive
       2 | #ifndef _LINUX_MM_H
         |  ^
   6 errors generated.


vim +2 include/linux/mm.h

^1da177e4c3f415 Linus Torvalds 2005-04-16 @2  #ifndef _LINUX_MM_H
^1da177e4c3f415 Linus Torvalds 2005-04-16  3  #define _LINUX_MM_H
^1da177e4c3f415 Linus Torvalds 2005-04-16  4  

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[David Hildenbrand (Arm)]

>>  
>>  static inline enum zone_type folio_zonenum(const struct folio *folio)
>>  {
>> +#if ZONES_WIDTH != 0
>> +	ASSERT_EXCLUSIVE_BITS(folio->flags, ZONES_MASK << ZONES_PGSHIFT);
>> +#endif
>>  	return memdesc_zonenum(folio->flags);
>>  }
>>  
> 
> Better to factor out a common macro alongside a comment for these two '#if'?

Yes.

And while looking at it, doesn't memdesc_section have similar problems? And
there are other callers of memdesc_zonenum we wouldn't handle. So the
macro approach is only partially helpful I thing.

Maybe we should just pass by reference and fixup all callers? Ends up the cleanest.

Untested:

From fb9b4e8c1d0419b960dc0cd4738d19d80d1fe14f Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Fri, 26 Jun 2026 11:06:39 +0200
Subject: [PATCH] mm: fix KASAN memdec_flags checks for zone/node/section

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 include/asm-generic/memory_model.h |  2 +-
 include/linux/mm.h                 | 23 +++++++++++++++--------
 include/linux/mm_inline.h          |  4 ++--
 include/linux/mmzone.h             | 24 ++++++++++++------------
 mm/page_alloc.c                    |  6 +++---
 mm/slab.h                          |  2 +-
 mm/sparse.c                        |  2 +-
 7 files changed, 35 insertions(+), 28 deletions(-)

diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index efa6610acbc79..f8404bc7773c2 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -53,7 +53,7 @@ static inline int pfn_valid(unsigned long pfn)
  */
 #define __page_to_pfn(pg)					\
 ({	const struct page *__pg = (pg);				\
-	int __sec = memdesc_section(__pg->flags);		\
+	int __sec = memdesc_section(&__pg->flags);		\
 	(unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec)));	\
 })
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 485df9c2dbddb..3111e4a6c9c4c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2286,22 +2286,28 @@ static inline int page_zone_id(struct page *page)
 }
 
 #ifdef NODE_NOT_IN_PAGE_FLAGS
-int memdesc_nid(memdesc_flags_t mdf);
+int memdesc_nid(const memdesc_flags_t *mdf);
+#elif defined(CONFIG_NUMA)
+static inline int memdesc_nid(const memdesc_flags_t *mdf)
+{
+	ASSERT_EXCLUSIVE_BITS(mdf->f, NODES_MASK << NODES_PGSHIFT);
+	return (mdf->f >> NODES_PGSHIFT) & NODES_MASK;
+}
 #else
-static inline int memdesc_nid(memdesc_flags_t mdf)
+static inline int memdesc_nid(const memdesc_flags_t *mdf)
 {
-	return (mdf.f >> NODES_PGSHIFT) & NODES_MASK;
+	return 0;
 }
 #endif
 
 static inline int page_to_nid(const struct page *page)
 {
-	return memdesc_nid(PF_POISONED_CHECK(page)->flags);
+	return memdesc_nid(&PF_POISONED_CHECK(page)->flags);
 }
 
 static inline int folio_nid(const struct folio *folio)
 {
-	return memdesc_nid(folio->flags);
+	return memdesc_nid(&folio->flags);
 }
 
 #ifdef CONFIG_NUMA_BALANCING
@@ -2541,12 +2547,13 @@ static inline void set_page_section(struct page *page, unsigned long section)
 	page->flags.f |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT;
 }
 
-static inline unsigned long memdesc_section(memdesc_flags_t mdf)
+static inline unsigned long memdesc_section(const memdesc_flags_t *mdf)
 {
-	return (mdf.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
+	ASSERT_EXCLUSIVE_BITS(mdf->f, SECTIONS_MASK << SECTIONS_PGSHIFT);
+	return (mdf->f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
 }
 #else /* !SECTION_IN_PAGE_FLAGS */
-static inline unsigned long memdesc_section(memdesc_flags_t mdf)
+static inline unsigned long memdesc_section(const memdesc_flags_t *mdf)
 {
 	return 0;
 }
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index a8430a7ae0544..efcddb9925add 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -650,7 +650,7 @@ static inline bool vma_has_recency(const struct vm_area_struct *vma)
 static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages)
 {
 	struct page *cur_page = pages[0];
-	unsigned long section = memdesc_section(cur_page->flags);
+	unsigned long section = memdesc_section(&cur_page->flags);
 	size_t i;
 
 	for (i = 1; i < nr_pages; i++) {
@@ -660,7 +660,7 @@ static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages)
 		 * In unproblematic kernel configs, page_to_section() == 0 and
 		 * the whole check will get optimized out.
 		 */
-		if (memdesc_section(cur_page->flags) != section)
+		if (memdesc_section(&cur_page->flags) != section)
 			break;
 	}
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ca27121871475..19e709d7a13de 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1272,31 +1272,31 @@ static inline bool zone_is_empty(const struct zone *zone)
 #define KASAN_TAG_MASK		((1UL << KASAN_TAG_WIDTH) - 1)
 #define ZONEID_MASK		((1UL << ZONEID_SHIFT) - 1)
 
-static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags)
+static inline enum zone_type memdesc_zonenum(const memdesc_flags_t *flags)
 {
-	ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT);
-	return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK;
+	ASSERT_EXCLUSIVE_BITS(flags->f, ZONES_MASK << ZONES_PGSHIFT);
+	return (flags->f >> ZONES_PGSHIFT) & ZONES_MASK;
 }
 
 static inline enum zone_type page_zonenum(const struct page *page)
 {
-	return memdesc_zonenum(page->flags);
+	return memdesc_zonenum(&page->flags);
 }
 
 static inline enum zone_type folio_zonenum(const struct folio *folio)
 {
-	return memdesc_zonenum(folio->flags);
+	return memdesc_zonenum(&folio->flags);
 }
 
 #ifdef CONFIG_ZONE_DEVICE
-static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
+static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf)
 {
 	return memdesc_zonenum(mdf) == ZONE_DEVICE;
 }
 
 static inline struct dev_pagemap *page_pgmap(const struct page *page)
 {
-	VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(page->flags), page);
+	VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(&page->flags), page);
 	return page_folio(page)->pgmap;
 }
 
@@ -1311,9 +1311,9 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page)
 static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
 						     const struct page *b)
 {
-	if (memdesc_is_zone_device(a->flags) != memdesc_is_zone_device(b->flags))
+	if (memdesc_is_zone_device(&a->flags) != memdesc_is_zone_device(&b->flags))
 		return false;
-	if (!memdesc_is_zone_device(a->flags))
+	if (!memdesc_is_zone_device(&a->flags))
 		return true;
 	return page_pgmap(a) == page_pgmap(b);
 }
@@ -1321,7 +1321,7 @@ static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
 extern void memmap_init_zone_device(struct zone *, unsigned long,
 				    unsigned long, struct dev_pagemap *);
 #else
-static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
+static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf)
 {
 	return false;
 }
@@ -1338,12 +1338,12 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page)
 
 static inline bool is_zone_device_page(const struct page *page)
 {
-	return memdesc_is_zone_device(page->flags);
+	return memdesc_is_zone_device(&page->flags);
 }
 
 static inline bool folio_is_zone_device(const struct folio *folio)
 {
-	return memdesc_is_zone_device(folio->flags);
+	return memdesc_is_zone_device(&folio->flags);
 }
 
 static inline bool is_zone_movable_page(const struct page *page)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ee902a468c2f5..020a97ca018e9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6904,15 +6904,15 @@ static void __free_contig_range_common(unsigned long pfn, unsigned long nr_pages
 			continue;
 		}
 
-		if (start && memdesc_section(page->flags) != start_sec) {
+		if (start && memdesc_section(&page->flags) != start_sec) {
 			free_prepared_contig_range(start, i - nr_start);
 			start = page;
 			nr_start = i;
-			start_sec = memdesc_section(page->flags);
+			start_sec = memdesc_section(&page->flags);
 		} else if (!start) {
 			start = page;
 			nr_start = i;
-			start_sec = memdesc_section(page->flags);
+			start_sec = memdesc_section(&page->flags);
 		}
 	}
 
diff --git a/mm/slab.h b/mm/slab.h
index bf2f87acf5e3a..1ae8e6084ba32 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -155,7 +155,7 @@ static inline void *slab_address(const struct slab *slab)
 
 static inline int slab_nid(const struct slab *slab)
 {
-	return memdesc_nid(slab->flags);
+	return memdesc_nid(&slab->flags);
 }
 
 static inline pg_data_t *slab_pgdat(const struct slab *slab)
diff --git a/mm/sparse.c b/mm/sparse.c
index 16ac6df3c89fa..8e38477645131 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -43,7 +43,7 @@ static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
 static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
 #endif
 
-int memdesc_nid(memdesc_flags_t mdf)
+int memdesc_nid(const memdesc_flags_t *mdf)
 {
 	return section_to_node_table[memdesc_section(mdf)];
 }
-- 
2.43.0


-- 
Cheers,

David