[PATCH 0/2] make hugetlb_optimize_vmemmap compatible with memmap_on_memory

[PATCH 0/2] make hugetlb_optimize_vmemmap compatible with memmap_on_memory

[Muchun Song]

This series makes hugetlb_optimize_vmemmap compatible with memmap_on_memory
and is based on next-20220518.
The reason refers to the patch 2's commit log.

Muchun Song (2):
  mm: memory_hotplug: enumerate all supported section flags
  mm: memory_hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP

 Documentation/admin-guide/kernel-parameters.txt | 22 ++++-----
 Documentation/admin-guide/sysctl/vm.rst         |  5 +-
 include/linux/kconfig.h                         |  1 +
 include/linux/memory_hotplug.h                  |  9 ----
 include/linux/mmzone.h                          | 64 +++++++++++++++++++++----
 mm/hugetlb_vmemmap.c                            | 28 ++++++++---
 mm/memory_hotplug.c                             | 28 +++++------
 mm/sparse.c                                     |  8 ++++
 8 files changed, 112 insertions(+), 53 deletions(-)

-- 
2.11.0

[PATCH 1/2] mm: memory_hotplug: enumerate all supported section flags

[Muchun Song]

We are almost running out of free slots, only one bit is available in the
worst case (powerpc with 256k pages).  However, there are still some free
slots on other architectures (e.g. x86_64 has 10 bits available, arm64
has 8 bits available with worst case of 64K pages).  We have hard coded
those numbers in code, it is inconvenient to use those bits on other
architectures except powerpc.  So transfer those section flags to
enumeration to make it easy to add new section flags in the future. Also,
move SECTION_TAINT_ZONE_DEVICE into the scope of CONFIG_ZONE_DEVICE
to save a bit on non-zone-device case.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/kconfig.h |  1 +
 include/linux/mmzone.h  | 47 +++++++++++++++++++++++++++++++++++++++--------
 mm/memory_hotplug.c     |  6 ++++++
 3 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
index 20d1079e92b4..7044032b9f42 100644
--- a/include/linux/kconfig.h
+++ b/include/linux/kconfig.h
@@ -10,6 +10,7 @@
 #define __LITTLE_ENDIAN 1234
 #endif
 
+#define __ARG_PLACEHOLDER_ 0,
 #define __ARG_PLACEHOLDER_1 0,
 #define __take_second_arg(__ignored, val, ...) val
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 299259cfe462..e0b7618d7212 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1422,16 +1422,47 @@ extern size_t mem_section_usage_size(void);
  *      (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the
  *      worst combination is powerpc with 256k pages,
  *      which results in PFN_SECTION_SHIFT equal 6.
- * To sum it up, at least 6 bits are available.
+ * To sum it up, at least 6 bits are available on all architectures.
+ * However, we can exceed 6 bits on some other architectures except
+ * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available
+ * with the worst case of 64K pages on arm64) if we make sure the
+ * exceeded bit is not applicable to powerpc.
  */
-#define SECTION_MARKED_PRESENT		(1UL<<0)
-#define SECTION_HAS_MEM_MAP		(1UL<<1)
-#define SECTION_IS_ONLINE		(1UL<<2)
-#define SECTION_IS_EARLY		(1UL<<3)
-#define SECTION_TAINT_ZONE_DEVICE	(1UL<<4)
-#define SECTION_MAP_LAST_BIT		(1UL<<5)
+#define ENUM_SECTION_FLAG(MAPPER)						\
+	MAPPER(MARKED_PRESENT)							\
+	MAPPER(HAS_MEM_MAP)							\
+	MAPPER(IS_ONLINE)							\
+	MAPPER(IS_EARLY)							\
+	MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE)				\
+	MAPPER(MAP_LAST_BIT)
+
+#define __SECTION_SHIFT_FLAG_MAPPER_0(x)
+#define __SECTION_SHIFT_FLAG_MAPPER_1(x)	SECTION_##x##_SHIFT,
+#define __SECTION_SHIFT_FLAG_MAPPER(x, ...)	\
+	__PASTE(__SECTION_SHIFT_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x)
+
+#define __SECTION_FLAG_MAPPER_0(x)
+#define __SECTION_FLAG_MAPPER_1(x)		SECTION_##x = BIT(SECTION_##x##_SHIFT),
+#define __SECTION_FLAG_MAPPER(x, ...)		\
+	__PASTE(__SECTION_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x)
+
+enum {
+	/*
+	 * Generate a series of enumeration flags like SECTION_$name_SHIFT.
+	 * Each entry in ENUM_SECTION_FLAG() macro will be generated to one
+	 * enumeration iff the 2nd parameter of MAPPER() is defined or absent.
+	 * The $name comes from the 1st parameter of MAPPER() macro.
+	 */
+	ENUM_SECTION_FLAG(__SECTION_SHIFT_FLAG_MAPPER)
+	/*
+	 * Generate a series of enumeration flags like:
+	 *   SECTION_$name = BIT(SECTION_$name_SHIFT)
+	 */
+	ENUM_SECTION_FLAG(__SECTION_FLAG_MAPPER)
+};
+
 #define SECTION_MAP_MASK		(~(SECTION_MAP_LAST_BIT-1))
-#define SECTION_NID_SHIFT		6
+#define SECTION_NID_SHIFT		SECTION_MAP_LAST_BIT_SHIFT
 
 static inline struct page *__section_mem_map_addr(struct mem_section *section)
 {
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1213d0c67a53..3b360eda933f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -672,12 +672,18 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon
 
 }
 
+#ifdef CONFIG_ZONE_DEVICE
 static void section_taint_zone_device(unsigned long pfn)
 {
 	struct mem_section *ms = __pfn_to_section(pfn);
 
 	ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE;
 }
+#else
+static inline void section_taint_zone_device(unsigned long pfn)
+{
+}
+#endif
 
 /*
  * Associate the pfn range with the given zone, initializing the memmaps
-- 
2.11.0

[PATCH 2/2] mm: memory_hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP

[Muchun Song]

For now, the feature of hugetlb_free_vmemmap is not compatible with the
feature of memory_hotplug.memmap_on_memory, and hugetlb_free_vmemmap
takes precedence over memory_hotplug.memmap_on_memory. However, someone
wants to make memory_hotplug.memmap_on_memory takes precedence over
hugetlb_free_vmemmap since memmap_on_memory makes it more likely to
succeed memory hotplug in close-to-OOM situations.  So the decision
of making hugetlb_free_vmemmap take precedence is not wise and elegant.
The proper approach is to have hugetlb_vmemmap.c do the check whether
the section which the HugeTLB pages belong to can be optimized.  If
the section's vmemmap pages are allocated from the added memory block
itself, hugetlb_free_vmemmap should refuse to optimize the vmemmap,
otherwise, do the optimization.  Then both kernel parameters are
compatible.  So this patch introduces SECTION_CANNOT_OPTIMIZE_VMEMMAP
to indicate whether the section could be optimized.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 22 +++++++++----------
 Documentation/admin-guide/sysctl/vm.rst         |  5 ++---
 include/linux/memory_hotplug.h                  |  9 --------
 include/linux/mmzone.h                          | 17 +++++++++++++++
 mm/hugetlb_vmemmap.c                            | 28 ++++++++++++++++++-------
 mm/memory_hotplug.c                             | 22 +++++++------------
 mm/sparse.c                                     |  8 +++++++
 7 files changed, 66 insertions(+), 45 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c087f578d9d8..5359ffb04a84 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1730,9 +1730,11 @@
 			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
 			the default is on.
 
-			This is not compatible with memory_hotplug.memmap_on_memory.
-			If both parameters are enabled, hugetlb_free_vmemmap takes
-			precedence over memory_hotplug.memmap_on_memory.
+			Note that the vmemmap pages may be allocated from the added
+			memory block itself when memory_hotplug.memmap_on_memory is
+			enabled, those vmemmap pages cannot be optimized even if this
+			feature is enabled.  Other vmemmap pages not allocated from
+			the added memory block itself do not be affected.
 
 	hung_task_panic=
 			[KNL] Should the hung task detector generate panics.
@@ -3077,10 +3079,12 @@
 			[KNL,X86,ARM] Boolean flag to enable this feature.
 			Format: {on | off (default)}
 			When enabled, runtime hotplugged memory will
-			allocate its internal metadata (struct pages)
-			from the hotadded memory which will allow to
-			hotadd a lot of memory without requiring
-			additional memory to do so.
+			allocate its internal metadata (struct pages,
+			those vmemmap pages cannot be optimized even
+			if hugetlb_free_vmemmap is enabled) from the
+			hotadded memory which will allow to hotadd a
+			lot of memory without requiring additional
+			memory to do so.
 			This feature is disabled by default because it
 			has some implication on large (e.g. GB)
 			allocations in some configurations (e.g. small
@@ -3090,10 +3094,6 @@
 			Note that even when enabled, there are a few cases where
 			the feature is not effective.
 
-			This is not compatible with hugetlb_free_vmemmap. If
-			both parameters are enabled, hugetlb_free_vmemmap takes
-			precedence over memory_hotplug.memmap_on_memory.
-
 	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
 			Format: <integer>
 			default : 0 <disable>
diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index 5c9aa171a0d3..d7374a1e8ac9 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -565,9 +565,8 @@ See Documentation/admin-guide/mm/hugetlbpage.rst
 hugetlb_optimize_vmemmap
 ========================
 
-This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter)
-is configured or the size of 'struct page' (a structure defined in
-include/linux/mm_types.h) is not power of two (an unusual system config could
+This knob is not available when the size of 'struct page' (a structure defined
+in include/linux/mm_types.h) is not power of two (an unusual system config could
 result in this).
 
 Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 20d7edf62a6a..e0b2209ab71c 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -351,13 +351,4 @@ void arch_remove_linear_mapping(u64 start, u64 size);
 extern bool mhp_supports_memmap_on_memory(unsigned long size);
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-bool mhp_memmap_on_memory(void);
-#else
-static inline bool mhp_memmap_on_memory(void)
-{
-	return false;
-}
-#endif
-
 #endif /* __LINUX_MEMORY_HOTPLUG_H */
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e0b7618d7212..3f73f24f394c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1434,6 +1434,7 @@ extern size_t mem_section_usage_size(void);
 	MAPPER(IS_ONLINE)							\
 	MAPPER(IS_EARLY)							\
 	MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE)				\
+	MAPPER(CANNOT_OPTIMIZE_VMEMMAP, CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP)	\
 	MAPPER(MAP_LAST_BIT)
 
 #define __SECTION_SHIFT_FLAG_MAPPER_0(x)
@@ -1471,6 +1472,22 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section)
 	return (struct page *)map;
 }
 
+#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+	ms->section_mem_map |= SECTION_CANNOT_OPTIMIZE_VMEMMAP;
+}
+
+static inline int section_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+	return (ms && (ms->section_mem_map & SECTION_CANNOT_OPTIMIZE_VMEMMAP));
+}
+#else
+static inline void section_mark_cannot_optimize_vmemmap(struct mem_section *ms)
+{
+}
+#endif
+
 static inline int present_section(struct mem_section *section)
 {
 	return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index fcd9f7872064..f12170520337 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -97,18 +97,32 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
 	return ret;
 }
 
+static unsigned int optimizable_vmemmap_pages(struct hstate *h,
+					      struct page *head)
+{
+	unsigned long pfn = page_to_pfn(head);
+	unsigned long end = pfn + pages_per_huge_page(h);
+
+	if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
+		return 0;
+
+	for (; pfn < end; pfn += PAGES_PER_SECTION) {
+		if (section_cannot_optimize_vmemmap(__pfn_to_section(pfn)))
+			return 0;
+	}
+
+	return hugetlb_optimize_vmemmap_pages(h);
+}
+
 void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
 {
 	unsigned long vmemmap_addr = (unsigned long)head;
 	unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
 
-	vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
+	vmemmap_pages = optimizable_vmemmap_pages(h, head);
 	if (!vmemmap_pages)
 		return;
 
-	if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
-		return;
-
 	static_branch_inc(&hugetlb_optimize_vmemmap_key);
 
 	vmemmap_addr	+= RESERVE_VMEMMAP_SIZE;
@@ -199,10 +213,10 @@ static struct ctl_table hugetlb_vmemmap_sysctls[] = {
 static __init int hugetlb_vmemmap_sysctls_init(void)
 {
 	/*
-	 * If "memory_hotplug.memmap_on_memory" is enabled or "struct page"
-	 * crosses page boundaries, the vmemmap pages cannot be optimized.
+	 * If "struct page" crosses page boundaries, the vmemmap pages cannot
+	 * be optimized.
 	 */
-	if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page)))
+	if (is_power_of_2(sizeof(struct page)))
 		register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
 
 	return 0;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3b360eda933f..7309694c4dee 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -43,30 +43,22 @@
 #include "shuffle.h"
 
 #ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-static int memmap_on_memory_set(const char *val, const struct kernel_param *kp)
-{
-	if (hugetlb_optimize_vmemmap_enabled())
-		return 0;
-	return param_set_bool(val, kp);
-}
-
-static const struct kernel_param_ops memmap_on_memory_ops = {
-	.flags	= KERNEL_PARAM_OPS_FL_NOARG,
-	.set	= memmap_on_memory_set,
-	.get	= param_get_bool,
-};
-
 /*
  * memory_hotplug.memmap_on_memory parameter
  */
 static bool memmap_on_memory __ro_after_init;
-module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444);
+module_param(memmap_on_memory, bool, 0444);
 MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
 
-bool mhp_memmap_on_memory(void)
+static inline bool mhp_memmap_on_memory(void)
 {
 	return memmap_on_memory;
 }
+#else
+static inline bool mhp_memmap_on_memory(void)
+{
+	return false;
+}
 #endif
 
 enum {
diff --git a/mm/sparse.c b/mm/sparse.c
index cb3bfae64036..1f353bf9ea6b 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -913,6 +913,14 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 	ms = __nr_to_section(section_nr);
 	set_section_nid(section_nr, nid);
 	__section_mark_present(ms, section_nr);
+	/*
+	 * Mark whole section as non-optimizable once there is a subsection
+	 * whose vmemmap pages are allocated from alternative allocator. The
+	 * early section is always optimizable since the early section's
+	 * vmemmap pages do not consider partially being populated.
+	 */
+	if (!early_section(ms) && altmap)
+		section_mark_cannot_optimize_vmemmap(ms);
 
 	/* Align memmap to section boundary in the subsection case */
 	if (section_nr_to_pfn(section_nr) != start_pfn)
-- 
2.11.0

Re: [PATCH 1/2] mm: memory_hotplug: enumerate all supported section flags

[kernel test robot]

Hi Muchun,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linux/master linus/master v5.18-rc7 next-20220519]
[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]

url:    https://github.com/intel-lab-lkp/linux/commits/Muchun-Song/make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory/20220519-204849
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: x86_64-randconfig-a016 (https://download.01.org/0day-ci/archive/20220519/202205192323.hAhv52wX-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project e00cbbec06c08dc616a0d52a20f678b8fbd4e304)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/94ab57cfaebf53ff1c57cc6c8b3ecc48bef31c5e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Muchun-Song/make-hugetlb_optimize_vmemmap-compatible-with-memmap_on_memory/20220519-204849
        git checkout 94ab57cfaebf53ff1c57cc6c8b3ecc48bef31c5e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 prepare

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from arch/x86/kernel/asm-offsets.c:9:
   In file included from include/linux/crypto.h:20:
   In file included from include/linux/slab.h:15:
   In file included from include/linux/gfp.h:6:
>> include/linux/mmzone.h:1506:44: error: use of undeclared identifier 'SECTION_TAINT_ZONE_DEVICE'
           unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE;
                                                     ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:97:11: warning: array index 3 is past the end of the array (which contains 1 element) [-Warray-bounds]
                   return (set->sig[3] | set->sig[2] |
                           ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:97:25: warning: array index 2 is past the end of the array (which contains 1 element) [-Warray-bounds]
                   return (set->sig[3] | set->sig[2] |
                                         ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:98:4: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
                           set->sig[1] | set->sig[0]) == 0;
                           ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:100:11: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
                   return (set->sig[1] | set->sig[0]) == 0;
                           ^        ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:113:11: warning: array index 3 is past the end of the array (which contains 1 element) [-Warray-bounds]
                   return  (set1->sig[3] == set2->sig[3]) &&
                            ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:
   In file included from include/linux/sched/signal.h:6:
   include/linux/signal.h:113:27: warning: array index 3 is past the end of the array (which contains 1 element) [-Warray-bounds]
                   return  (set1->sig[3] == set2->sig[3]) &&
                                            ^         ~
   arch/x86/include/asm/signal.h:24:2: note: array 'sig' declared here
           unsigned long sig[_NSIG_WORDS];
           ^
   In file included from arch/x86/kernel/asm-offsets.c:13:
   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:13:
   In file included from include/linux/cgroup.h:17:
   In file included from include/linux/fs.h:33:
   In file included from include/linux/percpu-rwsem.h:7:
   In file included from include/linux/rcuwait.h:6:


vim +/SECTION_TAINT_ZONE_DEVICE +1506 include/linux/mmzone.h

2d070eab2e8270 Michal Hocko 2017-07-06  1503  
1f90a3477df3ff Dan Williams 2021-02-25  1504  static inline int online_device_section(struct mem_section *section)
1f90a3477df3ff Dan Williams 2021-02-25  1505  {
1f90a3477df3ff Dan Williams 2021-02-25 @1506  	unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE;
1f90a3477df3ff Dan Williams 2021-02-25  1507  
1f90a3477df3ff Dan Williams 2021-02-25  1508  	return section && ((section->section_mem_map & flags) == flags);
1f90a3477df3ff Dan Williams 2021-02-25  1509  }
1f90a3477df3ff Dan Williams 2021-02-25  1510  

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