On Thu, Jan 15, 2026 at 10:20:11AM +0100, David Hildenbrand (Red Hat) wrote: > 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".
Saw: include/linux/balloon.h:25: * performing balloon page compaction. In order to sort out these racy scenarios include/linux/balloon.h:26: * and safely perform balloon's page compaction and migration we must, always, Documentation/mm/page_migration.rst:175:balloon-compaction infrastructure residing in the core kernel. At this commit so maybe a few more to chase up? > > While at it add some "/* CONFIG_BALLOON_MIGRATION */". > > Signed-off-by: David Hildenbrand (Red Hat) <[email protected]> Otherwise LGTM, so: Reviewed-by: Lorenzo Stoakes <[email protected]> > --- > 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 >
