1/*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
4 *
5 * Module Author: Heinz Mauelshagen
6 *
7 * This file is released under the GPL.
8 *
9 * Path-Selector registration.
10 */
11
12#ifndef	DM_PATH_SELECTOR_H
13#define	DM_PATH_SELECTOR_H
14
15#include <linux/device-mapper.h>
16
17#include "dm-mpath.h"
18
19/*
20 * We provide an abstraction for the code that chooses which path
21 * to send some io down.
22 */
23struct path_selector_type;
24struct path_selector {
25	struct path_selector_type *type;
26	void *context;
27};
28
29/* Information about a path selector type */
30struct path_selector_type {
31	char *name;
32	struct module *module;
33
34	unsigned int table_args;
35	unsigned int info_args;
36
37	/*
38	 * Constructs a path selector object, takes custom arguments
39	 */
40	int (*create) (struct path_selector *ps, unsigned argc, char **argv);
41	void (*destroy) (struct path_selector *ps);
42
43	/*
44	 * Add an opaque path object, along with some selector specific
45	 * path args (eg, path priority).
46	 */
47	int (*add_path) (struct path_selector *ps, struct dm_path *path,
48			 int argc, char **argv, char **error);
49
50	/*
51	 * Chooses a path for this io, if no paths are available then
52	 * NULL will be returned.
53	 */
54	struct dm_path *(*select_path) (struct path_selector *ps,
55					size_t nr_bytes);
56
57	/*
58	 * Notify the selector that a path has failed.
59	 */
60	void (*fail_path) (struct path_selector *ps, struct dm_path *p);
61
62	/*
63	 * Ask selector to reinstate a path.
64	 */
65	int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
66
67	/*
68	 * Table content based on parameters added in ps_add_path_fn
69	 * or path selector status
70	 */
71	int (*status) (struct path_selector *ps, struct dm_path *path,
72		       status_type_t type, char *result, unsigned int maxlen);
73
74	int (*start_io) (struct path_selector *ps, struct dm_path *path,
75			 size_t nr_bytes);
76	int (*end_io) (struct path_selector *ps, struct dm_path *path,
77		       size_t nr_bytes, u64 start_time);
78};
79
80/* Register a path selector */
81int dm_register_path_selector(struct path_selector_type *type);
82
83/* Unregister a path selector */
84int dm_unregister_path_selector(struct path_selector_type *type);
85
86/* Returns a registered path selector type */
87struct path_selector_type *dm_get_path_selector(const char *name);
88
89/* Releases a path selector  */
90void dm_put_path_selector(struct path_selector_type *pst);
91
92#endif
93