Subject: [PATCH v2 21/23] mm: rename CONFIG_BALLOON_COMPACTION to CONFIG_BALLOON_MIGRATION

From: "David Hildenbrand (Red Hat)" <[email-masked]>
Date: Thu, 15 Jan 2026 10:20:11 +0100

While compaction depends on migration, the other direction is not the
case. So let's make it clearer that this is all about migration of
balloon pages.

Adjust all comments/docs in the core to talk about "migration" instead
of "compaction".

While at it add some "/* CONFIG_BALLOON_MIGRATION */".

Signed-off-by: David Hildenbrand (Red Hat) <[email-masked]>
---
 Documentation/admin-guide/mm/memory-hotplug.rst |  8 ++++----
 arch/powerpc/platforms/pseries/cmm.c            |  8 ++++----
 drivers/misc/vmw_balloon.c                      |  8 ++++----
 drivers/virtio/virtio_balloon.c                 |  6 +++---
 include/linux/balloon.h                         |  2 +-
 include/linux/vm_event_item.h                   |  4 ++--
 mm/Kconfig                                      |  4 ++--
 mm/balloon.c                                    | 10 +++++-----
 mm/memory_hotplug.c                             |  4 ++--
 mm/migrate.c                                    |  2 +-
 mm/vmstat.c                                     |  4 ++--
 11 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 6581558fd0d7a..0207f87251421 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -603,11 +603,11 @@ ZONE_MOVABLE, especially when fine-tuning zone ratios:
   memory for metadata and page tables in the direct map; having a lot of offline
   memory blocks is not a typical case, though.
 
-- Memory ballooning without balloon compaction is incompatible with
-  ZONE_MOVABLE. Only some implementations, such as virtio-balloon and
-  pseries CMM, fully support balloon compaction.
+- Memory ballooning without support for balloon memory migration is incompatible
+  with ZONE_MOVABLE. Only some implementations, such as virtio-balloon and
+  pseries CMM, fully support balloon memory migration.
 
-  Further, the CONFIG_BALLOON_COMPACTION kernel configuration option might be
+  Further, the CONFIG_BALLOON_MIGRATION kernel configuration option might be
   disabled. In that case, balloon inflation will only perform unmovable
   allocations and silently create a zone imbalance, usually triggered by
   inflation requests from the hypervisor.
diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 7a3c4922685ab..8d83df12430f2 100644
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -494,7 +494,7 @@ static struct notifier_block cmm_mem_nb = {
 	.priority = CMM_MEM_HOTPLUG_PRI
 };
 
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 			   struct page *newpage, struct page *page,
 			   enum migrate_mode mode)
@@ -520,10 +520,10 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 	plpar_page_set_active(page);
 	return 0;
 }
-#else /* CONFIG_BALLOON_COMPACTION */
+#else /* CONFIG_BALLOON_MIGRATION */
 int cmm_migratepage(struct balloon_dev_info *b_dev_info, struct page *newpage,
 		    struct page *page, enum migrate_mode mode);
-#endif /* CONFIG_BALLOON_COMPACTION */
+#endif /* CONFIG_BALLOON_MIGRATION */
 
 /**
  * cmm_init - Module initialization
@@ -540,7 +540,7 @@ static int cmm_init(void)
 
 	balloon_devinfo_init(&b_dev_info);
 	b_dev_info.adjust_managed_page_count = true;
-	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
+	if (IS_ENABLED(CONFIG_BALLOON_MIGRATION))
 		b_dev_info.migratepage = cmm_migratepage;
 
 	rc = register_oom_notifier(&cmm_oom_nb);
diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 7fd3f709108c2..216a163959684 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1719,7 +1719,7 @@ static inline void vmballoon_debugfs_exit(struct vmballoon *b)
 #endif	/* CONFIG_DEBUG_FS */

-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 /**
  * vmballoon_migratepage() - migrates a balloon page.
  * @b_dev_info: balloon device information descriptor.
@@ -1803,11 +1803,11 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
 	up_read(&b->conf_sem);
 	return ret;
 }
-#else /* CONFIG_BALLOON_COMPACTION */
+#else /* CONFIG_BALLOON_MIGRATION */
 int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
 			  struct page *newpage, struct page *page,
 			  enum migrate_mode mode);
-#endif /* CONFIG_BALLOON_COMPACTION */
+#endif /* CONFIG_BALLOON_MIGRATION */
 
 static int __init vmballoon_init(void)
 {
@@ -1827,7 +1827,7 @@ static int __init vmballoon_init(void)
 		return error;
 
 	balloon_devinfo_init(&balloon.b_dev_info);
-	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
+	if (IS_ENABLED(CONFIG_BALLOON_MIGRATION))
 		balloon.b_dev_info.migratepage = vmballoon_migratepage;
 
 	INIT_LIST_HEAD(&balloon.huge_pages);
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index de8041c3285a1..4e549abe59ff1 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -802,7 +802,7 @@ static void report_free_page_func(struct work_struct *work)
 	}
 }
 
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 /*
  * virtballoon_migratepage - perform the balloon page migration on behalf of
  *			     a compaction thread.     (called under page lock)
@@ -851,7 +851,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 	mutex_unlock(&vb->balloon_lock);
 	return 0;
 }
-#endif /* CONFIG_BALLOON_COMPACTION */
+#endif /* CONFIG_BALLOON_MIGRATION */
 
 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
 				       unsigned long pages_to_free)
@@ -948,7 +948,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
 
 	if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 		vb->vb_dev_info.adjust_managed_page_count = true;
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 	vb->vb_dev_info.migratepage = virtballoon_migratepage;
 #endif
 	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
diff --git a/include/linux/balloon.h b/include/linux/balloon.h
index 82585542300d6..e8da95ca4ad48 100644
--- a/include/linux/balloon.h
+++ b/include/linux/balloon.h
@@ -45,7 +45,7 @@
 
 /*
  * Balloon device information descriptor.
- * This struct is used to allow the common balloon compaction interface
+ * This struct is used to allow the common balloon page migration interface
  * procedures to find the proper balloon device holding memory pages they'll
  * have to cope for page compaction / migration, as well as it serves the
  * balloon driver as a page book-keeper for its registered balloon devices.
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 92f80b4d69a6d..fca34d3473b6b 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -125,9 +125,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_MEMORY_BALLOON
 		BALLOON_INFLATE,
 		BALLOON_DEFLATE,
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 		BALLOON_MIGRATE,
-#endif
+#endif /* CONFIG_BALLOON_MIGRATION */
 #endif
 #ifdef CONFIG_DEBUG_TLBFLUSH
 		NR_TLB_REMOTE_FLUSH,	/* cpu tried to flush others' tlbs */
diff --git a/mm/Kconfig b/mm/Kconfig
index 0d13c1b36e1c1..460a148d5b71a 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -597,8 +597,8 @@ config MEMORY_BALLOON
 	bool
 
 #
-# support for memory balloon compaction
-config BALLOON_COMPACTION
+# support for memory balloon page migration
+config BALLOON_MIGRATION
 	bool "Allow for balloon memory migration"
 	default y
 	depends on MIGRATION && MEMORY_BALLOON
diff --git a/mm/balloon.c b/mm/balloon.c
index 5734dae81e318..8a21c6b9a7f0a 100644
--- a/mm/balloon.c
+++ b/mm/balloon.c
@@ -34,7 +34,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
 {
 	lockdep_assert_held(&balloon_pages_lock);
 	__SetPageOffline(page);
-	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION)) {
+	if (IS_ENABLED(CONFIG_BALLOON_MIGRATION)) {
 		SetPageMovableOps(page);
 		set_page_private(page, (unsigned long)balloon);
 	}
@@ -51,7 +51,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
 static inline void balloon_page_finalize(struct page *page)
 {
 	lockdep_assert_held(&balloon_pages_lock);
-	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
+	if (IS_ENABLED(CONFIG_BALLOON_MIGRATION))
 		set_page_private(page, 0);
 	/* PageOffline is sticky until the page is freed to the buddy. */
 }
@@ -153,7 +153,7 @@ struct page *balloon_page_alloc(void)
 {
 	gfp_t gfp_flags = __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 
-	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
+	if (IS_ENABLED(CONFIG_BALLOON_MIGRATION))
 		gfp_flags |= GFP_HIGHUSER_MOVABLE;
 	else
 		gfp_flags |= GFP_HIGHUSER;
@@ -232,7 +232,7 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
 }
 EXPORT_SYMBOL_GPL(balloon_page_dequeue);
 
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 
 static bool balloon_page_isolate(struct page *page, isolate_mode_t mode)
 
@@ -340,4 +340,4 @@ static int __init balloon_init(void)
 }
 core_initcall(balloon_init);
 
-#endif /* CONFIG_BALLOON_COMPACTION */
+#endif /* CONFIG_BALLOON_MIGRATION */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 389989a28abe0..bc805029da517 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -946,8 +946,8 @@ static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn
  * We rely on "present pages" instead of "managed pages", as the latter is
  * highly unreliable and dynamic in virtualized environments, and does not
  * consider boot time allocations. For example, memory ballooning adjusts the
- * managed pages when inflating/deflating the balloon, and balloon compaction
- * can even migrate inflated pages between zones.
+ * managed pages when inflating/deflating the balloon, and balloon page
+ * migration can even migrate inflated pages between zones.
  *
  * Using "present pages" is better but some things to keep in mind are:
  *
diff --git a/mm/migrate.c b/mm/migrate.c
index 4750a2ba15fef..1bf2cf8c44dd4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -88,7 +88,7 @@ static const struct movable_operations *page_movable_ops(struct page *page)
 	 * back to the buddy.
 	 */
 	if (PageOffline(page))
-		/* Only balloon compaction sets PageOffline pages movable. */
+		/* Only balloon page migration sets PageOffline pages movable. */
 		return offline_movable_ops;
 	if (PageZsmalloc(page))
 		return zsmalloc_movable_ops;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 6ae8891c9693e..e96a344ab5974 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1422,9 +1422,9 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_MEMORY_BALLOON
 	[I(BALLOON_INFLATE)]			= "balloon_inflate",
 	[I(BALLOON_DEFLATE)]			= "balloon_deflate",
-#ifdef CONFIG_BALLOON_COMPACTION
+#ifdef CONFIG_BALLOON_MIGRATION
 	[I(BALLOON_MIGRATE)]			= "balloon_migrate",
-#endif
+#endif /* CONFIG_BALLOON_MIGRATION */
 #endif /* CONFIG_MEMORY_BALLOON */
 #ifdef CONFIG_DEBUG_TLBFLUSH
 	[I(NR_TLB_REMOTE_FLUSH)]		= "nr_tlb_remote_flush",
-- 
2.52.0