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>
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
;
29 /* Information about a path selector type */
30 struct path_selector_type
{
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
58 struct dm_path
*(*select_path
) (struct path_selector
*ps
,
59 unsigned *repeat_count
,
63 * Notify the selector that a path has failed.
65 void (*fail_path
) (struct path_selector
*ps
, struct dm_path
*p
);
68 * Ask selector to reinstate a path.
70 int (*reinstate_path
) (struct path_selector
*ps
, struct dm_path
*p
);
73 * Table content based on parameters added in ps_add_path_fn
74 * or path selector status
76 int (*status
) (struct path_selector
*ps
, struct dm_path
*path
,
77 status_type_t type
, char *result
, unsigned int maxlen
);
79 int (*start_io
) (struct path_selector
*ps
, struct dm_path
*path
,
81 int (*end_io
) (struct path_selector
*ps
, struct dm_path
*path
,
85 /* Register a path selector */
86 int dm_register_path_selector(struct path_selector_type
*type
);
88 /* Unregister a path selector */
89 int dm_unregister_path_selector(struct path_selector_type
*type
);
91 /* Returns a registered path selector type */
92 struct path_selector_type
*dm_get_path_selector(const char *name
);
94 /* Releases a path selector */
95 void dm_put_path_selector(struct path_selector_type
*pst
);
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