v4.19.13 snapshot.
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
new file mode 100644
index 0000000..ef858d5
--- /dev/null
+++ b/mm/balloon_compaction.c
@@ -0,0 +1,177 @@
+/*
+ * mm/balloon_compaction.c
+ *
+ * Common interface for making balloon pages movable by compaction.
+ *
+ * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com>
+ */
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/balloon_compaction.h>
+
+/*
+ * balloon_page_alloc - allocates a new page for insertion into the balloon
+ * page list.
+ *
+ * Driver must call it to properly allocate a new enlisted balloon page.
+ * Driver must call balloon_page_enqueue before definitively removing it from
+ * the guest system. This function returns the page address for the recently
+ * allocated page or NULL in the case we fail to allocate a new page this turn.
+ */
+struct page *balloon_page_alloc(void)
+{
+ struct page *page = alloc_page(balloon_mapping_gfp_mask() |
+ __GFP_NOMEMALLOC | __GFP_NORETRY);
+ return page;
+}
+EXPORT_SYMBOL_GPL(balloon_page_alloc);
+
+/*
+ * balloon_page_enqueue - allocates a new page and inserts it into the balloon
+ * page list.
+ * @b_dev_info: balloon device descriptor where we will insert a new page to
+ * @page: new page to enqueue - allocated using balloon_page_alloc.
+ *
+ * Driver must call it to properly enqueue a new allocated balloon page
+ * before definitively removing it from the guest system.
+ * This function returns the page address for the recently enqueued page or
+ * NULL in the case we fail to allocate a new page this turn.
+ */
+void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
+ struct page *page)
+{
+ unsigned long flags;
+
+ /*
+ * Block others from accessing the 'page' when we get around to
+ * establishing additional references. We should be the only one
+ * holding a reference to the 'page' at this point.
+ */
+ BUG_ON(!trylock_page(page));
+ spin_lock_irqsave(&b_dev_info->pages_lock, flags);
+ balloon_page_insert(b_dev_info, page);
+ __count_vm_event(BALLOON_INFLATE);
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+ unlock_page(page);
+}
+EXPORT_SYMBOL_GPL(balloon_page_enqueue);
+
+/*
+ * balloon_page_dequeue - removes a page from balloon's page list and returns
+ * the its address to allow the driver release the page.
+ * @b_dev_info: balloon device decriptor where we will grab a page from.
+ *
+ * Driver must call it to properly de-allocate a previous enlisted balloon page
+ * before definetively releasing it back to the guest system.
+ * This function returns the page address for the recently dequeued page or
+ * NULL in the case we find balloon's page list temporarily empty due to
+ * compaction isolated pages.
+ */
+struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
+{
+ struct page *page, *tmp;
+ unsigned long flags;
+ bool dequeued_page;
+
+ dequeued_page = false;
+ spin_lock_irqsave(&b_dev_info->pages_lock, flags);
+ list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
+ /*
+ * Block others from accessing the 'page' while we get around
+ * establishing additional references and preparing the 'page'
+ * to be released by the balloon driver.
+ */
+ if (trylock_page(page)) {
+#ifdef CONFIG_BALLOON_COMPACTION
+ if (PageIsolated(page)) {
+ /* raced with isolation */
+ unlock_page(page);
+ continue;
+ }
+#endif
+ balloon_page_delete(page);
+ __count_vm_event(BALLOON_DEFLATE);
+ unlock_page(page);
+ dequeued_page = true;
+ break;
+ }
+ }
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+
+ 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;
+}
+EXPORT_SYMBOL_GPL(balloon_page_dequeue);
+
+#ifdef CONFIG_BALLOON_COMPACTION
+
+bool balloon_page_isolate(struct page *page, isolate_mode_t mode)
+
+{
+ 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);
+ b_dev_info->isolated_pages++;
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+
+ return true;
+}
+
+void balloon_page_putback(struct page *page)
+{
+ 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);
+ b_dev_info->isolated_pages--;
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+}
+
+
+/* move_to_new_page() counterpart for a ballooned page */
+int balloon_page_migrate(struct address_space *mapping,
+ struct page *newpage, struct page *page,
+ enum migrate_mode mode)
+{
+ struct balloon_dev_info *balloon = balloon_page_device(page);
+
+ /*
+ * We can not easily support the no copy case here so ignore it as it
+ * is unlikely to be use with ballon pages. See include/linux/hmm.h for
+ * user of the MIGRATE_SYNC_NO_COPY mode.
+ */
+ if (mode == MIGRATE_SYNC_NO_COPY)
+ return -EINVAL;
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+
+ return balloon->migratepage(balloon, newpage, page, mode);
+}
+
+const struct address_space_operations balloon_aops = {
+ .migratepage = balloon_page_migrate,
+ .isolate_page = balloon_page_isolate,
+ .putback_page = balloon_page_putback,
+};
+EXPORT_SYMBOL_GPL(balloon_aops);
+
+#endif /* CONFIG_BALLOON_COMPACTION */