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 */
23 struct path_selector_type;
24 struct path_selector {
25 struct path_selector_type *type;
26 void *context;
27 };
28
29 /* Information about a path selector type */
30 struct 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);
78 };
79
80 /* Register a path selector */
81 int dm_register_path_selector(struct path_selector_type *type);
82
83 /* Unregister a path selector */
84 int dm_unregister_path_selector(struct path_selector_type *type);
85
86 /* Returns a registered path selector type */
87 struct path_selector_type *dm_get_path_selector(const char *name);
88
89 /* Releases a path selector */
90 void dm_put_path_selector(struct path_selector_type *pst);
91
92 #endif