1 files changed, 93 insertions, 0 deletions
diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h
new file mode 100644
index 000000000000..732d06a84f85
--- /dev/null
+++ b/drivers/md/dm-path-selector.h
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen
+ *
+ * This file is released under the GPL.
+ *
+ * Path-Selector registration.
+ */
+
+#ifndef	DM_PATH_SELECTOR_H
+#define	DM_PATH_SELECTOR_H
+
+#include <linux/device-mapper.h>
+
+#include "dm-mpath.h"
+
+/*
+ * We provide an abstraction for the code that chooses which path
+ * to send some io down.
+ */
+struct path_selector_type;
+struct path_selector {
+	struct path_selector_type *type;
+	void *context;
+};
+
+/* Information about a path selector type */
+struct path_selector_type {
+	char *name;
+	struct module *module;
+
+	unsigned int table_args;
+	unsigned int info_args;
+
+	/*
+	 * Constructs a path selector object, takes custom arguments
+	 */
+	int (*create) (struct path_selector *ps, unsigned argc, char **argv);
+	void (*destroy) (struct path_selector *ps);
+
+	/*
+	 * Add an opaque path object, along with some selector specific
+	 * path args (eg, path priority).
+	 */
+	int (*add_path) (struct path_selector *ps, struct path *path,
+			 int argc, char **argv, char **error);
+
+	/*
+	 * Chooses a path for this io, if no paths are available then
+	 * NULL will be returned.
+	 *
+	 * repeat_count is the number of times to use the path before
+	 * calling the function again.  0 means don't call it again unless
+	 * the path fails.
+	 */
+	struct path *(*select_path) (struct path_selector *ps,
+				     unsigned *repeat_count);
+
+	/*
+	 * Notify the selector that a path has failed.
+	 */
+	void (*fail_path) (struct path_selector *ps, struct path *p);
+
+	/*
+	 * Ask selector to reinstate a path.
+	 */
+	int (*reinstate_path) (struct path_selector *ps, struct path *p);
+
+	/*
+	 * Table content based on parameters added in ps_add_path_fn
+	 * or path selector status
+	 */
+	int (*status) (struct path_selector *ps, struct path *path,
+		       status_type_t type, char *result, unsigned int maxlen);
+
+	int (*end_io) (struct path_selector *ps, struct path *path);
+};
+
+/* Register a path selector */
+int dm_register_path_selector(struct path_selector_type *type);
+
+/* Unregister a path selector */
+int dm_unregister_path_selector(struct path_selector_type *type);
+
+/* Returns a registered path selector type */
+struct path_selector_type *dm_get_path_selector(const char *name);
+
+/* Releases a path selector  */
+void dm_put_path_selector(struct path_selector_type *pst);
+
+#endif