+#ifdef CONFIG_BALLOON_COMPACTION
+static struct vfsmount *balloon_mnt;
+
+static int cmm_init_fs_context(struct fs_context *fc)
+{
+ return init_pseudo(fc, PPC_CMM_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type balloon_fs = {
+ .name = "ppc-cmm",
+ .init_fs_context = cmm_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
+ struct page *newpage, struct page *page,
+ enum migrate_mode mode)
+{
+ unsigned long flags;
+
+ /*
+ * loan/"inflate" the newpage first.
+ *
+ * We might race against the cmm_thread who might discover after our
+ * loan request that another page is to be unloaned. However, once
+ * the cmm_thread runs again later, this error will automatically
+ * be corrected.
+ */
+ if (plpar_page_set_loaned(newpage)) {
+ /* Unlikely, but possible. Tell the caller not to retry now. */
+ pr_err_ratelimited("%s: Cannot set page to loaned.", __func__);
+ return -EBUSY;
+ }
+
+ /* balloon page list reference */
+ get_page(newpage);
+
+ spin_lock_irqsave(&b_dev_info->pages_lock, flags);
+ balloon_page_insert(b_dev_info, newpage);
+ balloon_page_delete(page);
+ b_dev_info->isolated_pages--;
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+
+ /*
+ * activate/"deflate" the old page. We ignore any errors just like the
+ * other callers.
+ */
+ plpar_page_set_active(page);
+
+ /* balloon page list reference */
+ put_page(page);
+
+ return MIGRATEPAGE_SUCCESS;
+}
+
+static int cmm_balloon_compaction_init(void)
+{
+ int rc;
+
+ balloon_devinfo_init(&b_dev_info);
+ b_dev_info.migratepage = cmm_migratepage;
+
+ balloon_mnt = kern_mount(&balloon_fs);
+ if (IS_ERR(balloon_mnt)) {
+ rc = PTR_ERR(balloon_mnt);
+ balloon_mnt = NULL;
+ return rc;
+ }
+
+ b_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
+ if (IS_ERR(b_dev_info.inode)) {
+ rc = PTR_ERR(b_dev_info.inode);
+ b_dev_info.inode = NULL;
+ kern_unmount(balloon_mnt);
+ balloon_mnt = NULL;
+ return rc;
+ }
+
+ b_dev_info.inode->i_mapping->a_ops = &balloon_aops;
+ return 0;
+}
+static void cmm_balloon_compaction_deinit(void)
+{
+ if (b_dev_info.inode)
+ iput(b_dev_info.inode);
+ b_dev_info.inode = NULL;
+ kern_unmount(balloon_mnt);
+ balloon_mnt = NULL;
+}
+#else /* CONFIG_BALLOON_COMPACTION */
+static int cmm_balloon_compaction_init(void)
+{
+ return 0;
+}
+
+static void cmm_balloon_compaction_deinit(void)
+{
+}
+#endif /* CONFIG_BALLOON_COMPACTION */
+