ia64/kvm: compilation fix. export account_system_vtime.
[pv_ops_mirror.git] / drivers / md / dm-path-selector.h
blob27357b85d73d7495cbcb2d61e8522ac942317901
1 /*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
5 * Module Author: Heinz Mauelshagen
7 * This file is released under the GPL.
9 * Path-Selector registration.
12 #ifndef DM_PATH_SELECTOR_H
13 #define DM_PATH_SELECTOR_H
15 #include <linux/device-mapper.h>
17 #include "dm-mpath.h"
20 * We provide an abstraction for the code that chooses which path
21 * to send some io down.
23 struct path_selector_type;
24 struct path_selector {
25 struct path_selector_type *type;
26 void *context;
29 /* Information about a path selector type */
30 struct path_selector_type {
31 char *name;
32 struct module *module;
34 unsigned int table_args;
35 unsigned int info_args;
38 * Constructs a path selector object, takes custom arguments
40 int (*create) (struct path_selector *ps, unsigned argc, char **argv);
41 void (*destroy) (struct path_selector *ps);
44 * Add an opaque path object, along with some selector specific
45 * path args (eg, path priority).
47 int (*add_path) (struct path_selector *ps, struct dm_path *path,
48 int argc, char **argv, char **error);
51 * Chooses a path for this io, if no paths are available then
52 * NULL will be returned.
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.
58 struct dm_path *(*select_path) (struct path_selector *ps,
59 unsigned *repeat_count);
62 * Notify the selector that a path has failed.
64 void (*fail_path) (struct path_selector *ps, struct dm_path *p);
67 * Ask selector to reinstate a path.
69 int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
72 * Table content based on parameters added in ps_add_path_fn
73 * or path selector status
75 int (*status) (struct path_selector *ps, struct dm_path *path,
76 status_type_t type, char *result, unsigned int maxlen);
78 int (*end_io) (struct path_selector *ps, struct dm_path *path);
81 /* Register a path selector */
82 int dm_register_path_selector(struct path_selector_type *type);
84 /* Unregister a path selector */
85 int dm_unregister_path_selector(struct path_selector_type *type);
87 /* Returns a registered path selector type */
88 struct path_selector_type *dm_get_path_selector(const char *name);
90 /* Releases a path selector */
91 void dm_put_path_selector(struct path_selector_type *pst);
93 #endif