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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080047 int (*add_path) (struct path_selector *ps, struct dm_path *path,
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 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 * repeat_count is the number of times to use the path before
55 * calling the function again. 0 means don't call it again unless
56 * the path fails.
57 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080058 struct dm_path *(*select_path) (struct path_selector *ps,
Kiyoshi Ueda02ab8232009-06-22 10:12:27 +010059 unsigned *repeat_count,
60 size_t nr_bytes);
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
62 /*
63 * Notify the selector that a path has failed.
64 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080065 void (*fail_path) (struct path_selector *ps, struct dm_path *p);
Linus Torvalds1da177e2005-04-16 15:20:36 -070066
67 /*
68 * Ask selector to reinstate a path.
69 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080070 int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
72 /*
73 * Table content based on parameters added in ps_add_path_fn
74 * or path selector status
75 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080076 int (*status) (struct path_selector *ps, struct dm_path *path,
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 status_type_t type, char *result, unsigned int maxlen);
78
Kiyoshi Ueda02ab8232009-06-22 10:12:27 +010079 int (*start_io) (struct path_selector *ps, struct dm_path *path,
80 size_t nr_bytes);
81 int (*end_io) (struct path_selector *ps, struct dm_path *path,
82 size_t nr_bytes);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083};
84
85/* Register a path selector */
86int dm_register_path_selector(struct path_selector_type *type);
87
88/* Unregister a path selector */
89int dm_unregister_path_selector(struct path_selector_type *type);
90
91/* Returns a registered path selector type */
92struct path_selector_type *dm_get_path_selector(const char *name);
93
94/* Releases a path selector */
95void dm_put_path_selector(struct path_selector_type *pst);
96
97#endif