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
93