[PATCH v2 6/6] mm/balloon_compaction: general cleanup

[Konstantin Khlebnikov <koct9i@gmail.com>]

From: Konstantin Khlebnikov <k.khlebnikov@samsung.com>

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
---
 drivers/virtio/virtio_balloon.c    |   77 ++++---------
 include/linux/balloon_compaction.h |  127 ++++++---------------
 include/linux/migrate.h            |   11 --
 include/linux/pagemap.h            |   18 ---
 mm/balloon_compaction.c            |  214 ++++++++++++------------------------
 mm/migrate.c                       |   29 +----
 6 files changed, 134 insertions(+), 342 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 25ebe8e..c84d6a8 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -59,7 +59,7 @@ struct virtio_balloon
 	 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 	 * to num_pages above.
 	 */
-	struct balloon_dev_info *vb_dev_info;
+	struct balloon_dev_info vb_dev_info;
 
 	/* Synchronize access/update to this struct virtio_balloon elements */
 	struct mutex balloon_lock;
@@ -127,7 +127,7 @@ static void set_page_pfns(u32 pfns[], struct page *page)
 
 static void fill_balloon(struct virtio_balloon *vb, size_t num)
 {
-	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
+	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 
 	/* We can only do one array worth at a time. */
 	num = min(num, ARRAY_SIZE(vb->pfns));
@@ -163,15 +163,15 @@ static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
 	/* Find pfns pointing at start of each page, get pages and free them. */
 	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 		struct page *page = balloon_pfn_to_page(pfns[i]);
-		balloon_page_free(page);
 		adjust_managed_page_count(page, 1);
+		put_page(page);
 	}
 }
 
 static void leak_balloon(struct virtio_balloon *vb, size_t num)
 {
 	struct page *page;
-	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
+	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 
 	/* We can only do one array worth at a time. */
 	num = min(num, ARRAY_SIZE(vb->pfns));
@@ -353,12 +353,11 @@ static int init_vqs(struct virtio_balloon *vb)
 	return 0;
 }
 
-static const struct address_space_operations virtio_balloon_aops;
 #ifdef CONFIG_BALLOON_COMPACTION
 /*
  * virtballoon_migratepage - perform the balloon page migration on behalf of
  *			     a compation thread.     (called under page lock)
- * @mapping: the page->mapping which will be assigned to the new migrated page.
+ * @vb_dev_info: the balloon device
  * @newpage: page that will replace the isolated page after migration finishes.
  * @page   : the isolated (old) page that is about to be migrated to newpage.
  * @mode   : compaction mode -- not used for balloon page migration.
@@ -373,17 +372,13 @@ static const struct address_space_operations virtio_balloon_aops;
  * This function preforms the balloon page migration task.
  * Called through balloon_mapping->a_ops->migratepage
  */
-static int virtballoon_migratepage(struct address_space *mapping,
+static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 		struct page *newpage, struct page *page, enum migrate_mode mode)
 {
-	struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
-	struct virtio_balloon *vb;
+	struct virtio_balloon *vb = container_of(vb_dev_info,
+			struct virtio_balloon, vb_dev_info);
 	unsigned long flags;
 
-	BUG_ON(!vb_dev_info);
-
-	vb = vb_dev_info->balloon_device;
-
 	/*
 	 * In order to avoid lock contention while migrating pages concurrently
 	 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
@@ -395,42 +390,34 @@ static int virtballoon_migratepage(struct address_space *mapping,
 	if (!mutex_trylock(&vb->balloon_lock))
 		return -EAGAIN;
 
+	get_page(newpage); /* balloon reference */
+
 	/* balloon's page migration 1st step  -- inflate "newpage" */
 	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
-	balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
+	balloon_page_insert(vb_dev_info, newpage);
 	vb_dev_info->isolated_pages--;
 	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 	set_page_pfns(vb->pfns, newpage);
 	tell_host(vb, vb->inflate_vq);
 
-	/*
-	 * balloon's page migration 2nd step -- deflate "page"
-	 *
-	 * It's safe to delete page->lru here because this page is at
-	 * an isolated migration list, and this step is expected to happen here
-	 */
-	balloon_page_delete(page);
+	/* balloon's page migration 2nd step -- deflate "page" */
+	balloon_page_delete(page, true);
 	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 	set_page_pfns(vb->pfns, page);
 	tell_host(vb, vb->deflate_vq);
 
 	mutex_unlock(&vb->balloon_lock);
 
-	return MIGRATEPAGE_BALLOON_SUCCESS;
-}
+	put_page(page); /* balloon reference */
 
-/* define the balloon_mapping->a_ops callback to allow balloon page migration */
-static const struct address_space_operations virtio_balloon_aops = {
-			.migratepage = virtballoon_migratepage,
-};
+	return MIGRATEPAGE_SUCCESS;
+}
 #endif /* CONFIG_BALLOON_COMPACTION */
 
 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
-	struct address_space *vb_mapping;
-	struct balloon_dev_info *vb_devinfo;
 	int err;
 
 	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
@@ -446,30 +433,14 @@ static int virtballoon_probe(struct virtio_device *vdev)
 	vb->vdev = vdev;
 	vb->need_stats_update = 0;
 
-	vb_devinfo = balloon_devinfo_alloc(vb);
-	if (IS_ERR(vb_devinfo)) {
-		err = PTR_ERR(vb_devinfo);
-		goto out_free_vb;
-	}
-
-	vb_mapping = balloon_mapping_alloc(vb_devinfo,
-					   (balloon_compaction_check()) ?
-					   &virtio_balloon_aops : NULL);
-	if (IS_ERR(vb_mapping)) {
-		/*
-		 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
-		 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
-		 */
-		err = PTR_ERR(vb_mapping);
-		if (err != -EOPNOTSUPP)
-			goto out_free_vb_devinfo;
-	}
-
-	vb->vb_dev_info = vb_devinfo;
+	balloon_devinfo_init(&vb->vb_dev_info);
+#ifdef CONFIG_BALLOON_COMPACTION
+	vb->vb_dev_info.migratepage = virtballoon_migratepage;
+#endif
 
 	err = init_vqs(vb);
 	if (err)
-		goto out_free_vb_mapping;
+		goto out_free_vb;
 
 	vb->thread = kthread_run(balloon, vb, "vballoon");
 	if (IS_ERR(vb->thread)) {
@@ -481,10 +452,6 @@ static int virtballoon_probe(struct virtio_device *vdev)
 
 out_del_vqs:
 	vdev->config->del_vqs(vdev);
-out_free_vb_mapping:
-	balloon_mapping_free(vb_mapping);
-out_free_vb_devinfo:
-	balloon_devinfo_free(vb_devinfo);
 out_free_vb:
 	kfree(vb);
 out:
@@ -510,8 +477,6 @@ static void virtballoon_remove(struct virtio_device *vdev)
 
 	kthread_stop(vb->thread);
 	remove_common(vb);
-	balloon_mapping_free(vb->vb_dev_info->mapping);
-	balloon_devinfo_free(vb->vb_dev_info);
 	kfree(vb);
 }
 
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 09f8c5a..ad112fcc6 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -56,96 +56,58 @@
  * balloon driver as a page book-keeper for its registered balloon devices.
  */
 struct balloon_dev_info {
-	void *balloon_device;		/* balloon device descriptor */
-	struct address_space *mapping;	/* balloon special page->mapping */
 	unsigned long isolated_pages;	/* # of isolated pages for migration */
 	spinlock_t pages_lock;		/* Protection to pages list */
 	struct list_head pages;		/* Pages enqueued & handled to Host */
+	int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
+			struct page *page, enum migrate_mode mode);
 };
 
-extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
-extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
-extern struct balloon_dev_info *balloon_devinfo_alloc(
-						void *balloon_dev_descriptor);
-
-static inline void balloon_devinfo_free(struct balloon_dev_info *b_dev_info)
+static inline void balloon_devinfo_init(struct balloon_dev_info *b_dev_info)
 {
-	kfree(b_dev_info);
+	b_dev_info->isolated_pages = 0;
+	spin_lock_init(&b_dev_info->pages_lock);
+	INIT_LIST_HEAD(&b_dev_info->pages);
+	b_dev_info->migratepage = NULL;
 }
 
-/*
- * balloon_page_free - release a balloon page back to the page free lists
- * @page: ballooned page to be set free
- *
- * This function must be used to properly set free an isolated/dequeued balloon
- * page at the end of a sucessful page migration, or at the balloon driver's
- * page release procedure.
- */
-static inline void balloon_page_free(struct page *page)
-{
-	/*
-	 * Balloon pages always get an extra refcount before being isolated
-	 * and before being dequeued to help on sorting out fortuite colisions
-	 * between a thread attempting to isolate and another thread attempting
-	 * to release the very same balloon page.
-	 *
-	 * Before we handle the page back to Buddy, lets drop its extra refcnt.
-	 */
-	put_page(page);
-	__free_page(page);
-}
+extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
+extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
 
 /*
- * balloon_page_insert - insert a page into the balloon's page list and make
- *		         the page->mapping assignment accordingly.
- * @page    : page to be assigned as a 'balloon page'
- * @mapping : allocated special 'balloon_mapping'
- * @head    : balloon's device page list head
+ * balloon_page_insert - insert a page into the balloon's page list,
+ *			 mark and account it accordingly.
+ * @b_dev_info : pinter to ballon device
+ * @page       : page to be assigned as a 'balloon page'
  *
  * Caller must ensure the page is locked and the spin_lock protecting balloon
  * pages list is held before inserting a page into the balloon device.
  */
-static inline void balloon_page_insert(struct page *page,
-				       struct address_space *mapping,
-				       struct list_head *head)
+static inline void
+balloon_page_insert(struct balloon_dev_info *b_dev_info, struct page *page)
 {
 	__SetPageBalloon(page);
 	inc_zone_page_state(page, NR_BALLOON_PAGES);
-	page->mapping = mapping;
-	list_add(&page->lru, head);
+	set_page_private(page, (unsigned long)b_dev_info);
+	list_add(&page->lru, &b_dev_info->pages);
 }
 
 /*
  * balloon_page_delete - delete a page from balloon's page list and clear
- *			 the page->mapping assignement accordingly.
+ *			 the ballon page mark accordingly.
  * @page    : page to be released from balloon's page list
+ * @isolated: already isolated, do not delete from list
  *
  * Caller must ensure the page is locked and the spin_lock protecting balloon
  * pages list is held before deleting a page from the balloon device.
  */
-static inline void balloon_page_delete(struct page *page)
+static inline void balloon_page_delete(struct page *page, bool isolated)
 {
 	__ClearPageBalloon(page);
 	dec_zone_page_state(page, NR_BALLOON_PAGES);
-	page->mapping = NULL;
-	list_del(&page->lru);
-}
-
-#endif /* CONFIG_MEMORY_BALLOON */
-
-#ifdef CONFIG_BALLOON_COMPACTION
-
-extern bool balloon_page_isolate(struct page *page);
-extern void balloon_page_putback(struct page *page);
-extern int balloon_page_migrate(struct page *newpage,
-				struct page *page, enum migrate_mode mode);
-extern struct address_space
-*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
-			const struct address_space_operations *a_ops);
-
-static inline void balloon_mapping_free(struct address_space *balloon_mapping)
-{
-	kfree(balloon_mapping);
+	set_page_private(page, 0);
+	if (!isolated)
+		list_del(&page->lru);
 }
 
 /*
@@ -154,35 +116,25 @@ static inline void balloon_mapping_free(struct address_space *balloon_mapping)
  */
 static inline struct balloon_dev_info *balloon_page_device(struct page *page)
 {
-	struct address_space *mapping = page->mapping;
-	if (likely(mapping))
-		return mapping->private_data;
-
-	return NULL;
+	return (struct balloon_dev_info *)page_private(page);
 }
 
-static inline gfp_t balloon_mapping_gfp_mask(void)
-{
-	return GFP_HIGHUSER_MOVABLE;
-}
+#endif /* CONFIG_MEMORY_BALLOON */
 
-static inline bool balloon_compaction_check(void)
-{
-	return true;
-}
+#ifdef CONFIG_BALLOON_COMPACTION
+extern bool balloon_page_isolate(struct page *page);
+extern void balloon_page_putback(struct page *page);
 
-#else /* !CONFIG_BALLOON_COMPACTION */
+int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
+		unsigned long private, struct page *page,
+		int force, enum migrate_mode mode);
 
-static inline void *balloon_mapping_alloc(void *balloon_device,
-				const struct address_space_operations *a_ops)
+static inline gfp_t balloon_mapping_gfp_mask(void)
 {
-	return ERR_PTR(-EOPNOTSUPP);
+	return GFP_HIGHUSER_MOVABLE;
 }
 
-static inline void balloon_mapping_free(struct address_space *balloon_mapping)
-{
-	return;
-}
+#else /* !CONFIG_BALLOON_COMPACTION */
 
 static inline bool balloon_page_isolate(struct page *page)
 {
@@ -194,10 +146,11 @@ static inline void balloon_page_putback(struct page *page)
 	return;
 }
 
-static inline int balloon_page_migrate(struct page *newpage,
-				struct page *page, enum migrate_mode mode)
+static inline int balloon_page_migrate(new_page_t get_new_page,
+		free_page_t put_new_page, unsigned long private,
+		struct page *page, int force, enum migrate_mode mode)
 {
-	return 0;
+	return -EAGAIN;
 }
 
 static inline gfp_t balloon_mapping_gfp_mask(void)
@@ -205,9 +158,5 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
 	return GFP_HIGHUSER;
 }
 
-static inline bool balloon_compaction_check(void)
-{
-	return false;
-}
 #endif /* CONFIG_BALLOON_COMPACTION */
 #endif /* _LINUX_BALLOON_COMPACTION_H */
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 0a4604a..cf90776 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -13,18 +13,9 @@ typedef void free_page_t(struct page *page, unsigned long private);
  * Return values from addresss_space_operations.migratepage():
  * - negative errno on page migration failure;
  * - zero on page migration success;
- *
- * The balloon page migration introduces this special case where a 'distinct'
- * return code is used to flag a successful page migration to unmap_and_move().
- * This approach is necessary because page migration can race against balloon
- * deflation procedure, and for such case we could introduce a nasty page leak
- * if a successfully migrated balloon page gets released concurrently with
- * migration's unmap_and_move() wrap-up steps.
  */
 #define MIGRATEPAGE_SUCCESS		0
-#define MIGRATEPAGE_BALLOON_SUCCESS	1 /* special ret code for balloon page
-					   * sucessful migration case.
-					   */
+
 enum migrate_reason {
 	MR_COMPACTION,
 	MR_MEMORY_FAILURE,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 5ba1813..210b46b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -24,8 +24,7 @@ enum mapping_flags {
 	AS_ENOSPC	= __GFP_BITS_SHIFT + 1,	/* ENOSPC on async write */
 	AS_MM_ALL_LOCKS	= __GFP_BITS_SHIFT + 2,	/* under mm_take_all_locks() */
 	AS_UNEVICTABLE	= __GFP_BITS_SHIFT + 3,	/* e.g., ramdisk, SHM_LOCK */
-	AS_BALLOON_MAP  = __GFP_BITS_SHIFT + 4, /* balloon page special map */
-	AS_EXITING	= __GFP_BITS_SHIFT + 5, /* final truncate in progress */
+	AS_EXITING	= __GFP_BITS_SHIFT + 4, /* final truncate in progress */
 };
 
 static inline void mapping_set_error(struct address_space *mapping, int error)
@@ -55,21 +54,6 @@ static inline int mapping_unevictable(struct address_space *mapping)
 	return !!mapping;
 }
 
-static inline void mapping_set_balloon(struct address_space *mapping)
-{
-	set_bit(AS_BALLOON_MAP, &mapping->flags);
-}
-
-static inline void mapping_clear_balloon(struct address_space *mapping)
-{
-	clear_bit(AS_BALLOON_MAP, &mapping->flags);
-}
-
-static inline int mapping_balloon(struct address_space *mapping)
-{
-	return mapping && test_bit(AS_BALLOON_MAP, &mapping->flags);
-}
-
 static inline void mapping_set_exiting(struct address_space *mapping)
 {
 	set_bit(AS_EXITING, &mapping->flags);
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index a942081..3c8cb7a 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -11,32 +11,6 @@
 #include <linux/balloon_compaction.h>
 
 /*
- * balloon_devinfo_alloc - allocates a balloon device information descriptor.
- * @balloon_dev_descriptor: pointer to reference the balloon device which
- *                          this struct balloon_dev_info will be servicing.
- *
- * Driver must call it to properly allocate and initialize an instance of
- * struct balloon_dev_info which will be used to reference a balloon device
- * as well as to keep track of the balloon device page list.
- */
-struct balloon_dev_info *balloon_devinfo_alloc(void *balloon_dev_descriptor)
-{
-	struct balloon_dev_info *b_dev_info;
-	b_dev_info = kmalloc(sizeof(*b_dev_info), GFP_KERNEL);
-	if (!b_dev_info)
-		return ERR_PTR(-ENOMEM);
-
-	b_dev_info->balloon_device = balloon_dev_descriptor;
-	b_dev_info->mapping = NULL;
-	b_dev_info->isolated_pages = 0;
-	spin_lock_init(&b_dev_info->pages_lock);
-	INIT_LIST_HEAD(&b_dev_info->pages);
-
-	return b_dev_info;
-}
-EXPORT_SYMBOL_GPL(balloon_devinfo_alloc);
-
-/*
  * balloon_page_enqueue - allocates a new page and inserts it into the balloon
  *			  page list.
  * @b_dev_info: balloon device decriptor where we will insert a new page to
@@ -61,7 +35,7 @@ struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info)
 	 */
 	BUG_ON(!trylock_page(page));
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
-	balloon_page_insert(page, b_dev_info->mapping, &b_dev_info->pages);
+	balloon_page_insert(b_dev_info, page);
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 	unlock_page(page);
 	return page;
@@ -81,12 +55,10 @@ EXPORT_SYMBOL_GPL(balloon_page_enqueue);
  */
 struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
 {
-	struct page *page, *tmp;
+	struct page *page;
 	unsigned long flags;
-	bool dequeued_page;
 
-	dequeued_page = false;
-	list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
+	list_for_each_entry(page, &b_dev_info->pages, lru) {
 		/*
 		 * Block others from accessing the 'page' while we get around
 		 * establishing additional references and preparing the 'page'
@@ -94,98 +66,32 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
 		 */
 		if (trylock_page(page)) {
 			spin_lock_irqsave(&b_dev_info->pages_lock, flags);
-			/*
-			 * Raise the page refcount here to prevent any wrong
-			 * attempt to isolate this page, in case of coliding
-			 * with balloon_page_isolate() just after we release
-			 * the page lock.
-			 *
-			 * balloon_page_free() will take care of dropping
-			 * this extra refcount later.
-			 */
-			get_page(page);
-			balloon_page_delete(page);
+			balloon_page_delete(page, false);
 			spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 			unlock_page(page);
-			dequeued_page = true;
-			break;
+			return page;
 		}
 	}
 
-	if (!dequeued_page) {
-		/*
-		 * If we are unable to dequeue a balloon page because the page
-		 * list is empty and there is no isolated pages, then something
-		 * went out of track and some balloon pages are lost.
-		 * BUG() here, otherwise the balloon driver may get stuck into
-		 * an infinite loop while attempting to release all its pages.
-		 */
-		spin_lock_irqsave(&b_dev_info->pages_lock, flags);
-		if (unlikely(list_empty(&b_dev_info->pages) &&
-			     !b_dev_info->isolated_pages))
-			BUG();
-		spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
-		page = NULL;
-	}
-	return page;
+	/*
+	 * If we are unable to dequeue a balloon page because the page
+	 * list is empty and there is no isolated pages, then something
+	 * went out of track and some balloon pages are lost.
+	 * BUG() here, otherwise the balloon driver may get stuck into
+	 * an infinite loop while attempting to release all its pages.
+	 */
+	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
+	BUG_ON(list_empty(&b_dev_info->pages) && !b_dev_info->isolated_pages);
+	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(balloon_page_dequeue);
 
 #ifdef CONFIG_BALLOON_COMPACTION
-/*
- * balloon_mapping_alloc - allocates a special ->mapping for ballooned pages.
- * @b_dev_info: holds the balloon device information descriptor.
- * @a_ops: balloon_mapping address_space_operations descriptor.
- *
- * Driver must call it to properly allocate and initialize an instance of
- * struct address_space which will be used as the special page->mapping for
- * balloon device enlisted page instances.
- */
-struct address_space *balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
-				const struct address_space_operations *a_ops)
-{
-	struct address_space *mapping;
-
-	mapping = kmalloc(sizeof(*mapping), GFP_KERNEL);
-	if (!mapping)
-		return ERR_PTR(-ENOMEM);
-
-	/*
-	 * Give a clean 'zeroed' status to all elements of this special
-	 * balloon page->mapping struct address_space instance.
-	 */
-	address_space_init_once(mapping);
-
-	/*
-	 * Set mapping->flags appropriately, to allow balloon pages
-	 * ->mapping identification.
-	 */
-	mapping_set_balloon(mapping);
-	mapping_set_gfp_mask(mapping, balloon_mapping_gfp_mask());
-
-	/* balloon's page->mapping->a_ops callback descriptor */
-	mapping->a_ops = a_ops;
-
-	/*
-	 * Establish a pointer reference back to the balloon device descriptor
-	 * this particular page->mapping will be servicing.
-	 * This is used by compaction / migration procedures to identify and
-	 * access the balloon device pageset while isolating / migrating pages.
-	 *
-	 * As some balloon drivers can register multiple balloon devices
-	 * for a single guest, this also helps compaction / migration to
-	 * properly deal with multiple balloon pagesets, when required.
-	 */
-	mapping->private_data = b_dev_info;
-	b_dev_info->mapping = mapping;
-
-	return mapping;
-}
-EXPORT_SYMBOL_GPL(balloon_mapping_alloc);
 
 static inline void __isolate_balloon_page(struct page *page)
 {
-	struct balloon_dev_info *b_dev_info = page->mapping->private_data;
+	struct balloon_dev_info *b_dev_info = balloon_page_device(page);
 	unsigned long flags;
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 	list_del(&page->lru);
@@ -195,7 +101,7 @@ static inline void __isolate_balloon_page(struct page *page)
 
 static inline void __putback_balloon_page(struct page *page)
 {
-	struct balloon_dev_info *b_dev_info = page->mapping->private_data;
+	struct balloon_dev_info *b_dev_info = balloon_page_device(page);
 	unsigned long flags;
 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
 	list_add(&page->lru, &b_dev_info->pages);
@@ -203,12 +109,6 @@ static inline void __putback_balloon_page(struct page *page)
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 }
 
-static inline int __migrate_balloon_page(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode)
-{
-	return page->mapping->a_ops->migratepage(mapping, newpage, page, mode);
-}
-
 /* __isolate_lru_page() counterpart for a ballooned page */
 bool balloon_page_isolate(struct page *page)
 {
@@ -251,6 +151,57 @@ bool balloon_page_isolate(struct page *page)
 	return false;
 }
 
+int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
+			 unsigned long private, struct page *page,
+			 int force, enum migrate_mode mode)
+{
+	struct balloon_dev_info *balloon = balloon_page_device(page);
+	struct page *newpage;
+	int *result = NULL;
+	int rc = -EAGAIN;
+
+	if (!balloon || !balloon->migratepage)
+		return -EAGAIN;
+
+	newpage = get_new_page(page, private, &result);
+	if (!newpage)
+		return -ENOMEM;
+
+	if (!trylock_page(newpage))
+		BUG();
+
+	if (!trylock_page(page)) {
+		if (!force || mode != MIGRATE_SYNC)
+			goto out;
+		lock_page(page);
+	}
+
+	rc = balloon->migratepage(balloon, newpage, page, mode);
+
+	unlock_page(page);
+out:
+	unlock_page(newpage);
+
+	if (rc != -EAGAIN) {
+		dec_zone_page_state(page, NR_ISOLATED_FILE);
+		list_del(&page->lru);
+		put_page(page);
+	}
+
+	if (rc != MIGRATEPAGE_SUCCESS && put_new_page)
+		put_new_page(newpage, private);
+	else
+		put_page(newpage);
+
+	if (result) {
+		if (rc)
+			*result = rc;
+		else
+			*result = page_to_nid(newpage);
+	}
+	return rc;
+}
+
 /* putback_lru_page() counterpart for a ballooned page */
 void balloon_page_putback(struct page *page)
 {
@@ -271,31 +222,4 @@ void balloon_page_putback(struct page *page)
 	unlock_page(page);
 }
 
-/* move_to_new_page() counterpart for a ballooned page */
-int balloon_page_migrate(struct page *newpage,
-			 struct page *page, enum migrate_mode mode)
-{
-	struct address_space *mapping;
-	int rc = -EAGAIN;
-
-	/*
-	 * Block others from accessing the 'newpage' when we get around to
-	 * establishing additional references. We should be the only one
-	 * holding a reference to the 'newpage' at this point.
-	 */
-	BUG_ON(!trylock_page(newpage));
-
-	if (WARN_ON(!PageBalloon(page))) {
-		dump_page(page, "not movable balloon page");
-		unlock_page(newpage);
-		return rc;
-	}
-
-	mapping = page->mapping;
-	if (mapping)
-		rc = __migrate_balloon_page(mapping, newpage, page, mode);
-
-	unlock_page(newpage);
-	return rc;
-}
 #endif /* CONFIG_BALLOON_COMPACTION */
diff --git a/mm/migrate.c b/mm/migrate.c
index a4939b1..e6d0d2d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -873,18 +873,6 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
 		}
 	}
 
-	if (unlikely(PageBalloon(page))) {
-		/*
-		 * A ballooned page does not need any special attention from
-		 * physical to virtual reverse mapping procedures.
-		 * Skip any attempt to unmap PTEs or to remap swap cache,
-		 * in order to avoid burning cycles at rmap level, and perform
-		 * the page migration right away (proteced by page lock).
-		 */
-		rc = balloon_page_migrate(newpage, page, mode);
-		goto out_unlock;
-	}
-
 	/*
 	 * Corner case handling:
 	 * 1. When a new swap-cache page is read into, it is added to the LRU
@@ -952,19 +940,6 @@ static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
 
 	rc = __unmap_and_move(page, newpage, force, mode);
 
-#ifdef CONFIG_MEMORY_BALLOON
-	if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
-		/*
-		 * A ballooned page has been migrated already.
-		 * Now, it's the time to wrap-up counters,
-		 * handle the page back to Buddy and return.
-		 */
-		dec_zone_page_state(page, NR_ISOLATED_ANON +
-				    page_is_file_cache(page));
-		balloon_page_free(page);
-		return MIGRATEPAGE_SUCCESS;
-	}
-#endif
 out:
 	if (rc != -EAGAIN) {
 		/*
@@ -1139,6 +1114,10 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				rc = unmap_and_move_huge_page(get_new_page,
 						put_new_page, private, page,
 						pass > 2, mode);
+			else if (PageBalloon(page))
+				rc = balloon_page_migrate(get_new_page,
+						put_new_page, private,
+						page, pass > 2, mode);
 			else
 				rc = unmap_and_move(get_new_page, put_new_page,
 						private, page, pass > 2, mode);

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