1 files changed, 177 insertions, 0 deletions
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
new file mode 100644
index 000000000..ef858d547
--- /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 */