+ mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch added to -mm tree

+ mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/migrate: rework hotplug_memory_notifier() stub
has been added to the -mm tree.  Its filename is
     mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch

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------------------------------------------------------
From: Arnd Bergmann <arnd@arndb.de>
Subject: mm/migrate: rework hotplug_memory_notifier() stub

The previous change added a compile time warning for the
CONFIG_MEMORY_HOTPLUG=n case:

mm/migrate.c:3216:22: error: 'migrate_on_reclaim_callback' defined but not used [-Werror=unused-function]
 3216 | static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/migrate.c:3197:13: error: 'set_migration_target_nodes' defined but not used [-Werror=unused-function]
 3197 | static void set_migration_target_nodes(void)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~

Rework the hotplug_memory_notifier() stub implementation into an inline
function so it always references its argument but ignores it, leading the
compiler to silently drop the hotplug memory notifier function and further
code referenced from it.

To do this, the #ifdef around those functions need to be removed as well,
but this tends to help with readability and build coverage.

Link: https://lkml.kernel.org/r/20211013144029.2154629-1-arnd@kernel.org
Fixes: dd3e24b84bc1 ("mm/migrate: add CPU hotplug to demotion #ifdef")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/memory.h |    5 ++++-
 mm/migrate.c           |    6 +-----
 mm/page_ext.c          |    4 +---
 mm/slab.c              |    4 ++--
 4 files changed, 8 insertions(+), 11 deletions(-)

--- a/include/linux/memory.h~mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix
+++ a/include/linux/memory.h
@@ -160,7 +160,10 @@ int walk_dynamic_memory_groups(int nid,
 #define register_hotmemory_notifier(nb)		register_memory_notifier(nb)
 #define unregister_hotmemory_notifier(nb) 	unregister_memory_notifier(nb)
 #else
-#define hotplug_memory_notifier(fn, pri)	({ 0; })
+static inline int hotplug_memory_notifier(notifier_fn_t fn, int pri)
+{
+	return 0;
+}
 /* These aren't inline functions due to a GCC bug. */
 #define register_hotmemory_notifier(nb)    ({ (void)(nb); 0; })
 #define unregister_hotmemory_notifier(nb)  ({ (void)(nb); })
--- a/mm/migrate.c~mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix
+++ a/mm/migrate.c
@@ -3066,7 +3066,7 @@ void migrate_vma_finalize(struct migrate
 EXPORT_SYMBOL(migrate_vma_finalize);
 #endif /* CONFIG_DEVICE_PRIVATE */
 
-#if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_HOTPLUG_CPU)
+#if defined(CONFIG_HOTPLUG_CPU)
 /* Disable reclaim-based migration. */
 static void __disable_all_migrate_targets(void)
 {
@@ -3208,7 +3208,6 @@ static void set_migration_target_nodes(v
 	put_online_mems();
 }
 
-#if defined(CONFIG_MEMORY_HOTPLUG)
 /*
  * This leaves migrate-on-reclaim transiently disabled between
  * the MEM_GOING_OFFLINE and MEM_OFFLINE events.  This runs
@@ -3265,9 +3264,7 @@ static int __meminit migrate_on_reclaim_
 
 	return notifier_from_errno(0);
 }
-#endif /* CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_HOTPLUG_CPU
 /*
  * React to hotplug events that might affect the migration targets
  * like events that online or offline NUMA nodes.
@@ -3307,4 +3304,3 @@ static int __init migrate_on_reclaim_ini
 }
 late_initcall(migrate_on_reclaim_init);
 #endif /* CONFIG_HOTPLUG_CPU */
-#endif /* CONFIG_MEMORY_HOTPLUG || CONFIG_HOTPLUG_CPU */
--- a/mm/page_ext.c~mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix
+++ a/mm/page_ext.c
@@ -269,7 +269,7 @@ static int __meminit init_section_page_e
 	total_usage += table_size;
 	return 0;
 }
-#ifdef CONFIG_MEMORY_HOTPLUG
+
 static void free_page_ext(void *addr)
 {
 	if (is_vmalloc_addr(addr)) {
@@ -374,8 +374,6 @@ static int __meminit page_ext_callback(s
 	return notifier_from_errno(ret);
 }
 
-#endif
-
 void __init page_ext_init(void)
 {
 	unsigned long pfn;
--- a/mm/slab.c~mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix
+++ a/mm/slab.c
@@ -1095,7 +1095,7 @@ static int slab_offline_cpu(unsigned int
 	return 0;
 }
 
-#if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)
+#if defined(CONFIG_NUMA)
 /*
  * Drains freelist for a node on each slab cache, used for memory hot-remove.
  * Returns -EBUSY if all objects cannot be drained so that the node is not
@@ -1157,7 +1157,7 @@ static int __meminit slab_memory_callbac
 out:
 	return notifier_from_errno(ret);
 }
-#endif /* CONFIG_NUMA && CONFIG_MEMORY_HOTPLUG */
+#endif /* CONFIG_NUMA */
 
 /*
  * swap the static kmem_cache_node with kmalloced memory
_

Patches currently in -mm which might be from arnd@arndb.de are

mm-migrate-add-cpu-hotplug-to-demotion-ifdef-fix.patch
kasan-test-use-underlying-string-helpers.patch
posix-acl-avoid-wempty-body-warning.patch
hfs-hfsplus-use-warn_on-for-sanity-check.patch